breaking waves sailboat

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2 people with a mutual love for adventure, fall in love, buy a boat and set off in search of surf waves and a life full of experiences.

On a Mission

To find surf waves, somewhere hot, all to ourselves

Kiana. A 1989 Sceptre Sailboat that

Captain: Ben First Mate: Alie Deck Swabber: Bruce

To find remote surf breaks by sailboat

To help clean up the ocean by partnering with non profit organizations

Builder: Sceptre Yachts Designer: Hein Driehuyzen

Dimensions LOA: 41 ft  Draft 5 ft 8 in Beam 12 ft 8 in Displacement: 21500 lbs dry Headroom 6ft 5 in

Engine 55 HP Yanmar Inboard Diesel Cruising speed: 8 knots Max speed: 9knots

Tanks Fresh water: 95 Gallons Fuel: 3 Aluminum 32 Gallons Holding Tanks: 1

Accommodations  Double berths: 2 Single berths: 1

Construction Prolonged lead bolt on fin keel Skeg hung rudder Custom built 2 spreader sloop with cutter capabilities. Fixed running backstays. 

I remember sitting around a fire in Nanaimo BC when Ben told me his retirement dream. The stars were out and the warmth of the fire kept me warm as the sun set and seals poked their heads out of the water, daring Bruce to come into the ocean to chase them.

“I wanna buy a boat and sail south, where I can find warm water surf breaks all to myself”  he said. Painting a dreamy picture for me of exploration and surfing. 

I was a flight attendant at the time, my life was built around adventure, and I was set on living as if I wasn’t going to make it to retirement.

“what if we did it together?” I asked, “and what if we didn’t wait for retirement?” 

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Breaking Waves Sailing

Meet Ben and Alie. They bought a 41′ sailboat to live on and sail in British Columbia with their sandy boat dog Bruce. After sailing around Vancouver Island, and refitting the boat they set our sights to warmer water surf destinations. Presently on the Pacific coast of Mexico, both the boat and themselves as sailors, have come a long way. They’ve met their dream of surfing warm water waves off their sailboat, but they are only just getting started. They produce and release sailing lifestyle Youtube Videos every Sunday

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Breaking Waves

Waves in the lonely stretches of the open sea are little noticed by anyone but the occasional sailor. But once they reach shore, they become much more interesting. When waves break, or become unstable and topple forward, they thrill beachgoers and dramatically reshape the coastline.

Few people study breakers with more passion than surfers. As you investigate wave behavior in this lesson, you’ll learn that catching the perfect wave is as much a science as an art.

Study each image below to learn how waves move and break.

Catch a Wave

• What happens to a wave as it moves into shallow water? [ Hide Answer ] "> [ Check Answer ] When the water depth decreases to one half of a wave’s wavelength, the wave starts to “feel the bottom”. That means that the deepest water molecules set into circular motion by the wave’s energy run into the seafloor. This forces the wave to grow upwards, so wave height increases. The base of the wave is slowed down by friction against the sea bottom, while the top of the wave rushes ahead, so the wave crest begins to lean more and more forward until it topples over, and breaks on the shore.
• Describe how the slope of the seafloor controls the way a wave breaks. [ Hide Answer ] "> [ Check Answer ] On a gentle slope, waves begin to feel the bottom far from the shore. The waves grow slowly taller and lean forward, and foam spills down their fronts as they run up onto the beach. On a moderate slope, the waves get closer to shore before they break. Because the water shallows more rapidly, wave energy is rapidly concentrated into a small area, so the waves grow very tall and the crests curl far forward of the troughs. On a steep slope, the waves don’t interact with the bottom until they are almost right at the shore, so they don’t have time to build-up, and instead just surge far up the beach without breaking.
• Which type of breaker - spilling, plunging, or surging – will cause the most coastal erosion? Explain. [ Hide Answer ] "> [ Check Answer ] A surging breaker will cause the most erosion because it slams into the beach at full speed. Spilling and plunging breakers slow down as they drag across the seafloor, so their energy is dissipated over a wider zone.
• Which type of breaker - spilling, plunging, or surging – will deposit sand onshore and expand beaches? Explain. [ Hide Answer ] "> [ Check Answer ] Waves can move sand when their energy is in contact with the bottom. Spilling breakers spend the most time and energy dragging across the seabed, so they should be able to push more sand onto the beach. Surging waves hardly interact with the bottom at all, so they will have little effect on offshore sand.

Measure a Wave

• What is the wave period in the above animation? [ Hide Answer ] "> [ Check Answer ] The wave period in the animation is about 6 seconds
• What is the relationship between wavelength and period? As wavelength increases, how is wave period affected? [ Hide Answer ] "> [ Check Answer ] The wavelength is the distance between successive waves, and the period is the time it takes for waves to cover that distance.
• The approximate speed of a wave train can be calculated from the average period of the waves in the train, using a simple formula: speed (in knots, which are nautical miles per hour) = 1.5 x period (in seconds). If NOAA reports that a gale 400 nautical miles offshore has kicked up high waves with a period of 12 seconds, when should you go to the beach? [ Hide Answer ] "> [ Check Answer ] The speed of the wave train is 1.5 x 12, or 18 miles an hour. Since the waves are coming from 400 nautical miles away, they should star hitting the beach in just over 22 hours (400/18 = 22.22).
• What will happen to the wave period as the wave train reaches shallow water? [ Hide Answer ] "> [ Check Answer ] If the time it takes for successive wave crests to pass a point is constant even as the waves slow down, then the crests must get closer together, which means the wavelength decreases. As waves approach the shore, they bunch up, and the crests break in rapid succession.

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Breaking Waves

The equation for the speed, c, of a surface wave across the ocean is well known to physicists and is rather complicated. In deep water this equation reduces to a simple form that we have already encountered, c = Vgm p. So, in deep water the speed of a wave depends on wavelength, l. This fact influences the hull speed of a ship, as we have seen. In shallow water, the complicated equation for c reduces to a different limit, c = Vgh, where h is the water depth. So, in shallow water the wave speed does not depend on wavelength. Water is considered to be shallow if the depth is less than half the wavelength of the wave. Thus, if two waves are moving over the surface of a harbor that is 20 m deep, and the first wave has a wavelength of 100 m while the second has a wavelength of 15 m, the harbor appears shallow to the first wave and deep to the second.

Figure 7.5. If a wave approaches a shore obliquely, as seen here from a bird's eye view, a section of wave near the shore is in shallower water than a section further out and moves more slowly. So the wave changes direction to approach the shore less obliquely, i.e., more nearly parallel to the shore. In addition, the wavelength (the distance between the crests, shown here) decreases as the waves approach the shore.

There are several significant consequences of the shallow water limit for wave speed. Note that the wave slows down as the water becomes shallower. As a wave approaches a gently shelving beach, its speed slows (to zero, at h=0). The first consequence of this fact is that waves approaching a beach ''shape up'' to the shoreline; that is, they change direction so that they become more parallel with the shore.1 You can see how this works in figure 7.5. Wave speed, Vgh, decreases as a wave approaches the shore because h becomes less and less as it nears the shore; a wave approaching the shore at an oblique angle will straighten up.

The second consequence follows from the first. Again from figure 7.5 we see that because waves slow down as they approach a shore, they bunch together. But the energy of a wave has not dissipated significantly, and so the wave energy is contained in a smaller and smaller space as the waves bunch closer and closer together. This results in an increase in the wave amplitude. Think of water as an incompressible liquid (which is very nearly true). As the waves approach the shore, they become shorter. Because their volume does not change, they must grow taller. These

Figure 7.6. Stacked books on a conveyor belt will slip as shown if the conveyor slows down abruptly. Book 1 slows down almost as much as the conveyor because it has the weight of five books above it to hold it in place. Book 2 retains a little more of its speed because there is less weight above holding it down and more opportunity to slip (slippage occurs between conveyor and book 1, and also between books 1 and 2). Book 3 slips even more—i.e., retains more of its speed— and so on. Book 6 benefits from the slippage of all the books beneath it and so is least influenced by the conveyor deceleration. Breaking waves are analogous to the stack of books.

consequences of wave speed are familiar: as waves approach a beach they bunch together, shape up to the shoreline, and grow taller.

The physics of water waves backs up these everyday observations. We can show mathematically why the wave speed decreases in shallower water and how this slowing leads to increases in wave amplitude, etc. However, you have just seen that the underlying physics can be explained without math. A gradually shelving beach has another consequence for water waves that can be explained mathematically only with great difficulty but can be explained in physics terms quite easily, and that is the phenomenon of breaking waves. As waves slow and grow, they tip forward and break. Usually this wave breaking occurs when the amplitude reaches about three-quarters of the water depth (the surf zone of a beach). We can understand why this breaking phenomenon occurs in a couple of ways. First, from the equation for wave speed in shallow water (c = Vgh) we see that the crest of a wave will move faster than the trough

because h is greater at the top than at the bottom. The top of a wave gets ahead of the water beneath it, as shown in figure 7.6, and the wave breaks. Physically, we can see what is going on by imagining the wave to be like a stack of books on a conveyor belt. If the conveyor belt is suddenly slowed down, the books will continue trying to move forward, due to inertia. The result is shown in figure 7.6.

Oceanographers, hydrodynamicists, shore erosion ecologists, and all those intelligent people who are about to read this paragraph recognize four different types of breaking waves, named for the manner in which the wave crest collapses: spilling, plunging, surging, and collapsing. (Surfers cast expert eyes on waves that approach the shore, of course, but they are looking for different wave characteristics than are scientists, and so they give waves, and wave characteristics, a different set of names.*) Spilling waves are white-tops, generating a frothy top as the crest breaks up (fig. 7.7). The crests of plunging waves remain intact; they turn over (perhaps forming a "tube") and then crash dramatically; these are the surfer's waves. Surging waves occur on steeply sloping beaches; the base

* Beach breaks, corduroy, crumble, glassy, ground swells, point breaks, tubes . . .

of the wave reflects off the beach and back out to sea before the crest breaks properly. Collapsing waves are somewhere between plungers and surgers. The last two types are of no interest to surfers.

We have seen how the equation for wave speed in shallow water greatly influences the behavior and appearance of waves as they approach a beach. There is another physical effect of shallow water that is not so apparent if you are just looking at the waves but which is nevertheless of great practical importance. In figure 7.8 we have two waves merrily progressing from right to left. The deep-water wave maintains constant wave amplitude and wavelength. The wave approaching shore behaves differently, as we have seen. What about the individual water molecules? They do not move along with the wave but instead circulate as shown in figure 7.8. This is a surprising revelation to some people, who expect that, somehow, the water molecules just follow the wave, but this is not generally the case.* It cannot be so, if you think about it, because if the water moved in the wave direction, there would soon be no water left at the source of the wave disturbance.

Water molecule circulation becomes flattened near the sea bed, and in shallow water the flattened ellipses become stretched out almost to straight lines. This behavior of the individual particles of water is well understood mathematically and has been verified experimentally on many occasions. The fact that shallow water particles move almost horizontally, and over large distances, makes beaching waves dangerous. A tidal wave is a wave defined by this type of behavior. Tidal waves are dangerous because the water particles do not move in little circles or ellipses, but as a body in the wave direction when the wave passes by, and then as a body in the opposite direction as the wave is sucked back into the ocean.

Tsunamis are extreme examples of this type of wave. They originate in deep water, perhaps thousands of miles from shore, as very long wavelength waves with a lot of energy due usually to an underwater earthquake. The waves are so long (around 100 miles—160 km—in wavelength) that their enormous energy is not apparent out at sea. They will have low amplitude and may pass beneath a ship without anybody on

* Perhaps this misconception arises from looking at waves that break on shore; the molecules in these waves do indeed move along with the wave (or what is left of the wave) as it hits the beach, as we will see.

Figure 7.8. (a) A wave in deep water does not change shape: the crest amplitude and the distance between crests (the wavelength) are pretty much constant. Individual water particles move through circles or ellipses (in this case counterclockwise, since the wave is moving from right to left) as the wave passes over them. (b) Waves approaching a shore act very differently. Their amplitude increases and wavelength decreases. The front face of the wave becomes steeper and eventually breaks. Individual water particles describe elongated ellipses (more like straight lines), and they can move considerable distances from their equilibrium positions as the wave passes by.

board even noticing. But as they approach a shore, these waves become shorter and higher. Much higher. As shallow water waves, they move onto the shore as a wall of water, with all the water particles moving together, and then all receding together. This, of course, can devastate coastal towns and villages, as we all saw over the Christmas vacation in 2004, when a large tsunami in the Indian Ocean came ashore and took the lives of over 150,000 people, mostly in Sumatra. The rapidly approaching wall of water caused great damage, of course, but so did the

receding water. The volume of each tsunami wave is very large. For example, we now know that the wave trough that preceded the deadly waves in the 2004 tsunami caused the shoreline to recede 150 m (500 ft) just before the wave's arrival.

So, from figure 7.8 we see that those water particles which constitute a shallow water wave move along with the wave as it hits the beach. Most waves are not as damaging as tsunamis because they possess incomparably less energy, but they all behave in the same way. For windsurfers the behavior of shallow water waves is important because they are floating on these waves and are carried along by them. I could realistically ignore water speed when calculating the motion of sailing vessels in open ocean, but I will have to take it into account when considering how sailboards move in shallow water.

Continue reading here: Planing and the Need for Speed

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Readers' Questions

How does water move as waves pass?

As waves pass through a body of water, the individual water molecules move in a circular motion, but overall, the water moves in a forward-backward motion. This motion is called orbital motion. As a wave approaches the shore, the circular motion of water molecules becomes more elliptical, with the forward motion becoming more dominant. The water near the bottom slows down as it feels the friction of the seabed. The circular orbits become more distorted and eventually break, causing the wave to crash onto the shore. Water waves also transfer energy. As a wave passes, the water particles move in a cyclical pattern, with each particle moving up and down, but not generally moving in the same direction as the wave. This movement results in a transfer of energy from one water particle to another, causing the wave to propagate forward.

What makes waves break?

Waves break when they encounter an obstruction or shallow water, causing the wave energy to be compressed and to rise in height. There are several factors that contribute to waves breaking: Depth of water: When waves approach shallow water, the bottom of the wave interacts with the ocean floor. As the wave bottom becomes slower due to friction with the seabed, the wave top continues moving at its original speed. This difference in speed causes the wave to steepen and eventually break. Bottom shape and type: The shape and composition of the ocean floor play a role in how waves break. For example, when waves encounter a steep seabed, they tend to break more forcefully. A flat or gently sloping bottom can cause waves to break more gradually. Wave height: As waves grow higher and steeper, they are more likely to break. This is because the top of the wave becomes unstable and cannot support its own weight, leading to the wave crest collapsing. Wave period: The period is the time it takes for one complete wave to pass a given point. Longer period waves tend to refract and break further offshore, while shorter period waves break closer to the shore. Swell direction: Waves that approach a shoreline at an angle are more likely to break compared to waves that approach directly parallel to the shore. This is because the angled wave encounters shallower water sooner, causing it to break. Wind speed and direction: Strong winds blowing across the water's surface can generate larger waves that are more likely to break. The direction of the wind also influences the formation and breaking of waves. Wave steepness: Wave steepness refers to the ratio of wave height to wavelength. When wave steepness exceeds a certain threshold, typically around 1/7, the wave becomes unstable and breaks. These factors interact and influence each other, determining how waves break and the characteristics of surf conditions in a particular location.

How do water molecules move as part of deep ocean waves?

As part of deep ocean waves, water molecules move primarily in a circular motion known as orbital motion. Here's a detailed explanation of how water molecules move as part of deep ocean waves: Wave Formation: Deep ocean waves are generated by wind blowing across the water surface. The wind transfers its energy to the water, creating ripples that eventually grow into fully-formed waves. Circular Motion: When a deep ocean wave passes through a water molecule, it causes the molecule to move in a circular path known as an orbital motion. This circular motion occurs in a horizontal plane, primarily below the water surface. The Orbital Motion: In an orbital motion, water molecules move in a clockwise or counterclockwise direction, depending on the wave type. As the wave crest approaches, the water molecules move forward and rise. As the wave trough follows, the water molecules move backward and fall. Particle Trajectory: As the wave moves through the water, it doesn't carry the water particles with it. Instead, it transfers energy to nearby water molecules, creating a chain reaction of orbital motion. Each water molecule follows a circular path but doesn't move significantly in the direction of the wave propagation. Decaying Motion: As deep ocean waves propagate through the water, the orbital motion of water molecules diminishes with depth. The movement becomes less circular and more elliptical or spiral-shaped, gradually reducing the size and strength of the wave. It's important to note that while the motion of individual water molecules is circular, the overall propagation of the wave is forward. Deep ocean waves can travel vast distances, yet the motion of water molecules remains primarily localized near the surface.

Where waves break book?

I'm sorry, but I'm not familiar with a book called "Where Waves Break." It is possible that this book doesn't exist or may be a lesser-known publication. If you have any other questions or if there's anything else I can help you with, please let me know.

Why do waves change as they approach shorelines?

Waves change as they approach shorelines due to a phenomenon called wave shoaling. When waves move from deep water to shallower water near the shoreline, their speed decreases and their wavelength decreases. At the same time, their wave height increases. This change occurs because the bottom of the ocean or sea floor affects the movement of waves. In deep water, the waves have more space to propagate, and the energy is distributed over a larger area, resulting in longer wavelengths and smaller wave heights. However, as the waves approach shallower water, the bottom of the ocean starts to interfere with the wave motion. As waves encounter the sea floor, their energy is compressed into a smaller area, causing the wave to slow down. This reduction in wave speed causes the wavelength to decrease. Additionally, the bottom friction also causes the water particles near the bottom to reduce their motion, while the upper particles continue their forward movement. This results in an increase in wave height. The combination of decreasing wavelength and increasing wave height causes the wave to "bunch up" near the shore, becoming steeper and often breaking. Ultimately, the wave breaks when it becomes too steep for the water particles to maintain their shape. This breaking wave releases its energy onto the shoreline, resulting in the familiar crashing sound and the movement of water and sediment onto the beach. Therefore, as waves approach shorelines, their characteristics change due to wave shoaling, resulting in shorter wavelengths, higher wave heights, and often breaking waves.

What is breaking wave in sailing?

A breaking wave in sailing refers to a wave that has reached its maximum height and is cresting or collapsing forward, creating white water and spray. Breaking waves can occur in various conditions, including rough weather, strong winds, or when waves encounter shallow water or obstacles such as sandbars or reefs. In sailing, encountering breaking waves can be challenging as it can cause a boat to pitch and roll, affecting stability and potentially leading to capsizing or damage if not managed properly. Sailors must carefully navigate through breaking waves or adjust their course to minimize the impact on the boat and crew.

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Storm Tactics for Heavy Weather Sailing

• By Bill Gladstone
• Updated: November 15, 2021

Storm tactics can be roughly defined as the ways to handle a storm once you’re in it. There are several proven choices, all of which intend to keep either the bow or stern pointing toward the waves. No one tactic will work best for all sailboats in all conditions. As skipper, it will be up to you to consider the best approach for your vessel, procure the right equipment, and practice with it before it’s needed.

Here we look at some active storm options that might work when conditions are still manageable and you want to actively control and steer the boat. Crew fatigue is a serious consideration when using active tactics.

Forereaching

Although not often mentioned as a tactic, it can be highly effective for combating brief squalls or moderate-duration storms. Here’s how to set up your boat for forereaching: Roll the jib away (especially if you have a large roller-furler genoa set); reef the main down to the second or third reef position; and sail on a closehauled course, concentrating on keeping the boat flat. It will be a comfortable ride, everyone will be relatively happy, and you will be making 2 to 3 knots on a close reach. Check your course over ground because increased leeway will cause your track to be much lower. This is a possibly useful tactic to claw off a lee shore. Note that not all boats will be at ease forereaching, so you’d better experiment with it ahead of time. Catamarans in particular will lurch and demonstrate much-increased leeway.

Motorsailing

Sometimes it’s necessary from a time or safety perspective to stow the jib and fire up the iron genny instead. Motorsailing lets you point high and make progress to windward. Motoring with no sails will not work well (or at all, in some cases), particularly in big seas, but a reefed mainsail will provide lateral stability and extra power. Trim the main, head up high enough to control your angle of heel, set the autopilot, and keep a lookout. Fuel consumption makes this a short-term option.

Here’s a tip: Make sure cooling water is pumping through the engine. On some sailboats, the water intake lifts out of the water when heeled. A further difficulty is that the pitching boat might stir sediment off the bottom of the fuel tank, which can, in turn, clog the fuel filter.

Running off and drogues

Sailing under storm jib and a deeply reefed mainsail or storm trysail provides the most control. If you don’t have storm sails, a reefed jib will give you the power to steer and control your boat in the waves. The boat must be steered actively to maintain control because no autopilot will be able to do this.

If excessive speed is a problem and steering becomes difficult, towing a drogue will slow the boat. A retrieval line should be set from the head of the drogue for when it is time to bring it back on board. If you don’t have a drogue, trailing warps might help slow the boat.

In a storm of longer duration, or when conditions become otherwise unmanageable, the situation might call for a skipper to consider passive storm tactics. When you are exhausted and you just want to quiet down the boat and maybe get some rest, there are other boathandling options available, depending on the sea state and the ­equipment you have onboard.

Heaving to can be an excellent heavy-weather tactic, though some boats fare better than others. Wouldn’t it be great if during a heavy-weather episode you could just slow everything way down? Imagine a short respite with a reduced amount of motion from the relentless pitching and pounding. A chance to regroup, make a meal, or check over the boat. Well, you can.

Heaving to allows you to “park” in open water. Hove-to trim has the jib trimmed aback (that is, to the wrong side), the reefed main eased, and the helm lashed down to leeward. The easiest way to do this is to trim the jib sheet hard and then tack the boat, leaving the sheet in place. Trimmed this way, the jib pushes the bow down. As the bow turns off the wind, the main fills and the boat moves forward. With the helm lashed down, the rudder turns the boat toward the wind. As the main goes soft, the jib once again takes over, pushing the bow down. The main refills, and the rudder pushes the bow into the wind again.

RELATED: Safety at Sea: Mental Preparations Contribute to Positive Outcomes

Achieving this balance will require some fine-­tuning, depending on the wind strength, your boat design and the sails you have. You might, for example, need to furl the jib most of the way in to match the wind strength. Trimming the main will ensure that the bow is at an angle to the waves, ideally pointing 40 to 60 degrees off. Modern fin-keeled boats do not heave to as well as more-traditional full-keel designs.

When hove to, the boat won’t actually stop. It will lie, as noted, about 40 to 60 degrees off the wind, sailing at 1 or 2 knots, and making leeway (sliding to leeward). Beware of chafe. When hove to, the jib’s clew or sheet will be up against the shroud and might experience wear damage. Monitor this regularly, and change the position of the sheet occasionally. You might not want to heave to for an extended time.

Deploying a sea anchor

A sea anchor is a small parachute deployed on a line off the bow. A sea anchor helps keep the bow pointed up into the waves so the boat won’t end up beam to the seas. Light displacement boats will pitch violently in high seas, and chafe and damage might occur to the bow, so setting up a bridle and leading it aft through a snatch block will allow the boat to lie at an angle to the waves, providing a more comfortable ride. A big concern when using a sea anchor is the load on the rudder as the waves slam the boat backward. Chafe on the sea-anchor bridle is another big factor, so the bridle must be tended regularly.

Remember, if you and your vessel are caught out in heavy-weather conditions, as a skipper, you must show leadership by setting an example, watching over your crew, offering relief and help to those who need it, and giving encouragement. Remember too, discomfort and fear can lead to fatigue, diminished performance, and poor decision-making. Don’t compromise the safety of the boat and crew to escape discomfort.

Few people get to ­experience the full fury of a storm. Advances in weather forecasting, routing and communications greatly improve your odds of avoiding heavy weather at sea, but you’re likely to experience it at some point, so think ahead of time about the tactics and tools available to keep your crew and vessel safe.

Heavy weather might not be pleasant, but it is certainly memorable, and it will make you a better sailor. Take the time to marvel at the forces of nature; realize that the boat is stronger than you think.

Happy sailing, and may all your storms be little ones!

This story is an edited excerpt from the American Sailing Association’s recently released manual, Advanced Cruising & Seamanship , by Bill Gladstone, produced in collaboration with North U. It has been edited for design purposes and style. You can find out more at asa.com.

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Ocean Wave Basics

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A closer look at how waves form and what affects them will help you make smarter boating decisions.

It's helpful to understand the science behind wave formation, but it's even more important to know how your boat handles in waves coming from different directions. (Photo: Getty Images/SGoodwin4813)

Waves develop as a result of wind blowing for a certain amount of time (duration) over a certain distance (fetch). The stronger the wind and the longer the fetch, the higher the waves become over time. Ocean waves that move beyond the place from which they were generated become deep-water swells, underlying the local, wind-generated surface waves.

Ocean swells can travel great distances and inevitably encounter other swells of different lengths and heights, which were generated in other areas and are traveling in different directions. A typical sea state is made up of a mixture of deep-water swells and waves, which all combine to form the apparent chaotic ocean surface known as the wave spectrum.

Periodically, wave peaks will coincide, producing especially large waves; at other times they will virtually cancel each other out and form relatively small waves. So there is no single "wave height" that will describe all waves at a given place and time.

What Wave Height Means

Because there is never only one wave height, oceanographers use a statistical analysis to forecast "significant wave height" (SWH). This is defined as the average of the largest one-third of all waves, and it is the wave height that an experienced observer will typically report. The actual wave height at a given time and place can be much higher, as much as twice the forecast SWH. With a forecast SWH of 10 feet, the mean wave height would be 6.4 feet; the highest 10 percent of waves would be 12.7 feet; the highest 1 percent of waves would be 16.7 feet; and the maximum wave height to be expected would be 20 feet.

What Influences Wave Shape, Height, And Direction?

Wind waves are independent of the swell and add to the wave height. The result is called "combined seas (CS)." The National Weather Service considers CS equal to SWH. Waves are defined by four components: height (trough to crest), length (distance between crests), period (time elapsed from the passage of one crest to the next), and steepness. Steepness is the ratio between height and length. When wave steepness exceeds 1:7, the wave will begin to break — resulting in whitecaps. This generally happens in 12 to 15 knots of wind.

Near-Shore Influences On Deep-Water Waves

There are a number of things that will change the shape, height, and direction of deep-water swell.

Reflection happens when waves bounce back from an obstruction and combine with still-approaching waves. Reflected waves have been seen as far as 15 miles off the California coast where the shore falls steeply into the ocean.

Refraction is a change in direction as a wave encounters shallower water near the shore. The shallower water slows the wave, causing a bending (or refraction) that favors parallel wave fronts to approach the shoreline. Near a headland, refraction focuses wave energy at the tip of the point. Near islands, waves often wrap all the way around the island. And when waves rejoin in the lee of the island, they can augment each other to form larger, sometimes breaking waves.

When current opposes the wind, waves can build quickly to steep and dangerous proportions. Common examples include the Gulf Stream, the Agulhas current, and places where prevailing winds oppose tidal currents (San Francisco Bay, or the Bay of Fundy during a strong ebb).

Unusual or "rogue" waves are the combination of smaller wave peaks into larger-than-normal waves. They often appear from a different direction than the main wave pattern as sudden breaking seas. They can cause unexpected damage in an otherwise manageable sea state. Seamounts such as the Cortes Bank, which is 100 miles off the coast of San Diego, can create 14-foot (and occasionally much larger) breakers in the middle of an otherwise calm sea.

Shoaling And Lee Shores

When a deep-water wave reaches shallower water, its characteristics will change. The apparent "movement" of a deep-water wave is actually a moving pulse of pressure; individual water particles rotate within the wave crest as the pulse passes. Once a wave "feels the bottom," it slows down. The period remains unchanged, however, so the wave becomes slower, shorter, and taller. As water depth decreases, wave height increases, until the wave becomes unstable and breaks. The water particles in a breaking wave no longer rotate within the wave crest; instead they rush down its face.

If the breaker forms gradually (a slower-moving wave hits a gently sloping beach), the waves will form "spilling" breakers with the water tumbling down the sloping face of the wave. If the breaker forms quickly (a faster-moving wave hits a more steeply sloping shoreline), then a "plunging" breaker forms; the face becomes vertical, curls, and then collapses into the trough. This is the classic surfing wave. The plunging breaker generally contains more energy and is therefore more dangerous.

Breaking waves of any height are much more dangerous than even significantly larger ocean swells. The surface force of a breaking wave has the tendency to turn a boat broadside – the "log effect." A breaking wave equal in height to the beam of the boat is likely to capsize a boat.

Depths At Which Breakers Will Form

The critical question for boaters is at what depth breakers will form, particularly when approaching a lee shore. A series of calculations well beyond the scope of this article will answer that question exactly by calculating three important factors: the wave's size and steepness, the depth of the water, and the shape of the bottom contour.

Fortunately, for the boater approaching a lee shore, there are several rules of thumb to help you calculate safe water depth for a given weather forecast. One of the most reliable is professional offshore navigator Stan Honey's rule (see "Practical Takeaways" below). So for a forecasted 15-foot swell and 7-foot wind-wave, the minimum safe water depth would be 55 feet (add 15 and 7 to get 22, then multiply by 2.5).

Practical Takeaways

• To figure Stan Honey's rule for safe water depth, especially when rounding headlands or traveling near shore, take the maximum forecast swell PLUS the wind-wave height, and MULTIPLY that number by 2.5.
• When you see a report that the "standard wave height" on a given day is 10 feet, this means most of the waves you'll encounter will be below that height, but some will be 12, 16, and 20 feet.
• Whitecaps begin to occur when the wind is between 12 to 15 knots.
• What you see now may not be what you get later. For example, going out an inlet in the morning may be flat calm. But a series of waves emanating from a faraway storm and reaching the shore in the afternoon may be humping up near the coast and creating dangerous mayhem. Add to that an outgoing tide against the waves and things could be even worse.
• Here's an example of "wave wrap," as described in the article: There's a great breeze and you pick a nice spot to anchor for the afternoon on the lee side of a little island. Perfect. But instead of your bow pointing into that cool breeze, it starts rolling, as with a beam sea. This is wave wrap, when waves meet an obstruction (in this case, your island), part around it, and meet to create turbulence on the lee side. So now your bow points one way while the waves are coming from the other. Compensate for this by rigging a bridle to hold your boat into the apparent wind, or find a calmer anchorage.
• Don't pick a fight head on. When meeting waves, it's usually best to slow down, giving ample power to steer but not much speed. Fall off, putting the waves to the starboard or port of the bow rather than dead on. Don't put them on the beam.
• When running with waves, there's greater risk than running into them. Waves from astern may raise your stern giving less steering power. Worse, they may be faster than you're running, giving less bite for the rudder. The risk, especially for small, light boats, is they'll put your bow under, causing a flip, broach, or bow flooding.
• If you're offshore and getting a storm with a lot of wind, it's seldom best to head for shallow water. Waves meeting shallow water can quickly get much steeper and even start breaking. If it's safe and practical, stay in deeper water till the storm or squall passes.
• You can't accurately predict the height of every wave. So before the going gets tough, secure the boat so water can't get in the cabin and things don't go flying. Have crew prepare by donning life jackets and other appropriate safety gear.

— The Editors

There are many factors affecting wave formation and a wide variety of possible wave heights and characteristics for any given sea state. Know how your boat will handle waves from the bow, the quarter, and abeam, and be prepared to orient your vessel to best advantage for any given sea-state.

Whenever possible, avoid shallow water and lee shores, and remember:

• You will not be able to see breaking waves as you approach from the deep-water side.
• The point of breaking can change significantly and rapidly as the wave form changes.
• You can suddenly be inside the "breaker zone" when you thought you were well outside of it.

Excerpted from US Sailing's Safety at Sea: A Guide to Safety Under Sail and Personal Survival . ussailing.org

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Yachting Monthly

• Digital edition

How to interpret wave patterns for comfortable sailing

• May 8, 2020

Ken Endean explains how to read the water to find fair tides and avoid rough water

Photo 1: A torrential tide, but apparently flowing both ways - see the yacht in the background. Credit: Ken Endean

Which way is the tide flowing, and how do we tell?

We could look at a tidal diamond on a chart, or at the arrows in a tidal atlas, but these sources are not infallible, particularly near irregular coastlines where the streams may be deflected or even reverse direction.

It’s often helpful to go back to basics and simply look at the sea, beginning with the water around moored objects, although this may pose more questions when sailing in waves .

For instance, in photo 1 (above), the tide past the buoy is obviously rushing from right to left, but the moored yacht against the far shore is in a current flowing from left to right.

This is where things get interesting, because that photo also shows that the ‘texture’ of the water surface changes between the buoy and the yacht.

In the foreground, there is a fairly uniform carpet of small waves but near the yacht the surface has smooth patches, caused by turbulence.

That area of water is an inshore eddy that is flowing counter to the main stream.

It is unlikely to be shown by a chart’s tidal diamond, or even in a tidal atlas, but could be very helpful to any skipper who wants to cheat the tide.

For a closer view of a similar effect, photo 2 was taken on Loch Linnhe, while beating through the Corran Narrows against the tide.

Photo 2: Cheating the tide by staying out of the main stream. Credit: Ken Endean

Corran Point is close to starboard, behind the jib, and the flood tide is flowing clear of the point, leaving an inshore area of turbulence that is not flowing anywhere in particular.

The boundary between the two is quite distinct, with a thin line of foam, and the yacht is being sailed through the turbulence to avoid the adverse current.

Tide plus wind

Under windier conditions turbulence would be masked by larger waves, but changes in currents will also change the wave shapes.

In photo 3, we are beating past Land’s End, towards Cape Cornwall, riding on the first of the north-going tide.

Photo 3: Wind against tide producing small, splashy waves. Credit: Ken Endean

The wind is only at the top end of Force 3, and yet the sea seems to be covered by white horses and the waves look brittle, too short and steep for that strength of breeze: a classic case of wind-against-tide.

On weaker currents, that effect would be less noticeable.

Even so, a change in wave form should be obvious at a boundary between two currents.

Photo 4A was taken on the seaward side of Hurst Spit (see Diagram 1).

Photo 4A: An inshore current is flowing against the wind, away from the camera. Credit: Ken Endean

In the distance, the Solent ebb was pouring out past the fort on Hurst Point.

Part of that tidal stream was running out through the North Channel, past the photographer, but it had begun to swing away as a developing inshore eddy flowed back along the beach, towards the fort.

That eddy was clearly visible as an area of slightly larger waves, but it is less obvious in a still photograph because the eye and brain normally take account of movement in the water when distinguishing between different wave patterns, and a still picture omits that information.

Diagram 1: Tidal eddy close to Hurst Spit. Credit: Maxine Heath

That is a problem when writing about waves, because printed photos do not capture all their character.

However, for Photo 4B the camera programme was set to ‘Dramatic Tone’, which creates a lurid image but also accentuates wave patterns so that the outer edge of the eddy is crisply defined, much as it appears to the naked eye.

Photo 4B: With the camera set to ‘dramatic tone’ the current becomes more obvious. Credit: Ken Endean

For a yacht heading into the Solent , with a crew who can read the surface clues, it should be possible to make progress against the main tide by short-tacking within that eddy until close to the fort, when the curve of the spit might allow her to hold starboard tack on a close fetch past the point – potentially a valuable tactic when racing.

In both examples, off Land’s End and at Hurst, the wind is blowing against the current and that influences the waves in several ways.

First, it increases the apparent wind speed over the water, although in most instances this will only amount to a few knots – less than one wind force.

Continues below…

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It also increases the apparent wave fetch, because waves that are moving against a contrary current will take longer to reach anywhere and this allows them to grow larger before they arrive.

But a third phenomenon often has a greater influence: when waves that are rolling upstream meet an adverse current they are immediately foreshortened as the crests bunch closer together.

That compresses the wave energy into a smaller distance, so the waves also grow higher and the combination of shorter wavelength and greater height makes them much steeper.

Coming to a halt

Shortening the wavelength means the waves move more slowly through the water, and if they run up against a very strong contrary current this may be sufficient to completely halt the movement of wave energy.

The wave crests themselves do not stop still but become very steep and then fade away or break – generally a bit of both – leaving calmer water upstream and creating a typical overfall pattern as in photo 5.

Wave patterns: Photo 5: A sharp overfall where the tide pours across the Spur Bank in the River Bandon. Credit: Ken Endean

There the tide is flowing from right to left, into the estuary of the River Bandon, the wind is blowing against the tide and the overfall has appeared where the current pours over a submerged bank.

The overfall pattern indicates the tidal stream direction and marks the bank, which is why the fishing boat has been able to ignore the buoy and steer outside the navigation channel.

Waves can also be stopped when they are moving downstream on a current.

Most of us will be familiar with wave reflection when waves rebound from harbour walls, typically producing a ‘spiky’ water surface as in photo 6, where the reflected waves are smacking against the incoming waves so that the crests appear to be jumping up and down.

Photo 6: Clapotic crests where waves are reflecting from the Cobb and Lyme Regis. Credit: Ken Endean

The same phenomenon, known as clapotic waves, can occur when waves and current are moving in the same direction but abruptly run into a different current.

In photo 7, we are back off Hurst Point, but sailing into the Solent with the flood tide and a following wind (see Diagram 2), and the little jumpy waves are just like those in photo 6.

Photo 7: More clapotic crests at a meeting of tidal streams, in Hurst Narrows. Credit: Ken Endean

Two flood streams are converging here and if we swing the camera to the left, towards the fort on Hurst Point, in photo 8 we can also see an abrupt meeting of currents.

Photo 8: Here the waves are reflecting off the smooth water of a counter current. Credit: Ken Endean

A vigorous tidal eddy, its surface smoothed by turbulence, is surging out from behind the point and the incoming waves, carried on the strong flood, are being stopped and reflected at the edge of this eddy.

Therefore, if we meet clapotic waves when sailing downwind , we are probably about to run into slack water or an adverse current.

Diagram 2: Clapotic waves at the convergence of currents. Credit: Maxine Heath

When the waves are large – either in rough weather or when they arrive as ocean swell – overfalls and clapotic effects are capable of generating particularly violent sea states, but there are some important differences.

When the waves break in overfalls they curl over in an upstream direction and break heavily.

Clapotic waves, on the other hand, are inclined to fling their crests directly upwards.

While a big crest might then dump itself on a yacht it is potentially less dangerous because it is less likely to roll the boat over.

Even so, it could be unpleasant.

A few years ago we were beating west from Cherbourg and taking advantage of a west-flowing counter-current off Omonville while big waves rolled past in the opposite direction on the main east-going tide.

Where those waves collided with the edge of the counter-current the clapotic crests were huge and one of them swamped our cockpit, with some water penetrating the cabin.

If we try that route again, we’ll remember to keep the hatch firmly shut!

Bending the waves

Both overfalls and clapotic waves have a useful side-effect, in that they concentrate wave energy in one place so that other patches of sea become calmer – such as the area upstream of an overfall.

Oblique interaction between waves and adverse currents produces a similar result, even if the waves are not stopped.

Where waves meet a tongue of contrary current, as in Diagram 3, they bend into the current and then move across it diagonally.

Diagram 3: Waves captured and retained by an adverse current. Credit: Maxine Heath

When they reach slack water on the far side, they can travel forward more quickly but that causes the crests to turn back into the current, so that they are effectively trapped and continue to roll upstream, while more waves alongside the current may swing on to it.

The tongue of current therefore absorbs wave energy and becomes rougher while the water beside it becomes calmer, as in photo 9.

Photo 9: On the Owenboy River, the breaking crests are all on the main flood stream and the slack water by the bank is almost flat. Credit: Ken Endean

This phenomenon makes the edge of the current more prominent, which is helpful if you either want to stay in it, or to stay out of it and sail on the calmer water.

There is also a valuable breakwater effect.

On a Scottish cruise, we called in at the small port of Girvan and moored in the harbour basin, which is separated from the river channel by a training wall.

A stiff north-westerly wind was sending waves straight into the harbour and London Apprentice moved uneasily against the pontoon, fenders squeaking.

Later, while we were eating supper, we noticed that the motion had ceased and the water in the basin was almost flat.

It was an hour after high water , the tide was running out of the river channel, and the incoming waves were now locked into that current, rolling straight up the river without agitating the basin (Diagram 4).

Diagram 4: Girvan Harbour, showing wave pattern on the ebb tide. Credit: Maxine Heath

Photographs could not show the whole scene and to illustrate the phenomenon I needed a scale model, which we later found at Lynmouth.

Here the small harbour is very similar to Girvan, with a basin separated from a river channel by a training wall, and Photo 10, taken from the high edge of Exmoor while the tide was ebbing, shows most of the incoming waves rolling up the river channel, against the current, while the harbour basin is relatively undisturbed.

Photo 10: Lynmouth Harbour, with incoming waves trapped in the ebb current from the river. Credit: Ken Endean

I have again used ‘dramatic tone’ to emphasise the wave patterns, including a distinct band of smooth water close alongside the current.

Similar clearly defined current boundaries are often seen on estuaries and even on the open sea, giving keen sailors more precise information than they would find in a tidal atlas.

The breakwater effect is also important for cruisers, because it provides a temporary period of calm.

Within the Channel Islands, popular beach anchorages experience Atlantic swell that wraps around the islands but they often become quieter when the tidal races are flowing towards the south-west, against the incoming swell.

The strong currents between the islands appear to be absorbing some of the wave energy because the waves at the shore decrease but then increase again when the streams reverse.

Crews who have landed by tender on an open beach may be surprised by rougher conditions if they attempt to relaunch after the tide has turned.

Select your sea state

Ken Endean is an inshore pilotage enthusiast who has made a close study of coastal sea conditions around the British Isles

A knowledge of surface wave patterns can be used in various ways.

Small waves that change shape to make currents visible can indicate a favourable stream for a fast passage.

With larger waves, if we have made ourselves familiar with the tidal streams it is possible to predict areas of rough water and avoid them.

In some places we’ll even find calmer water that is flowing the way we want to go.

Speed or comfort, or both: the sea sometimes allows us a choice.

Which waves could be dangerous?

This article has focused on the visible interactions between waves and currents, which help us to make best use of tidal streams.

Those interactions sometimes affect safety, by creating very rough water, and a lot depends on the wavelengths.

In complex currents, short waves often make a fuss without being dangerous, while tranquil ocean swells can become surprisingly violent, although very long waves may grow more impressive without turning nasty.

Rather than attempt to illustrate those points by going for a sail with my camera in seriously rough conditions, I should like to use a couple more photos in which the waves can serve as small-scale models.

Photo 11 was taken while racing through Jack Sound with a strong spring tide.

Photo 11: A fast reach through Jack Sound on a powerful spring ebb with a nearly flat sea. Credit: Ken Endean

This is a place where pilot books promise chaos and doom unless the passage is made at slack water, but although the surface could be described as ‘seething’, there is nothing in that picture that resembles a threat.

In photo 12 we are running against the stream, through a small tidal race off Peterhead that doesn’t seem to merit a mention in any pilot book.

Photo 12: Lumpy waves in North Sea overfalls. Credit: Ken Endean

The waves in this picture are larger and the yacht is being flung about vigorously, spilling wind from the sails, yet only the tips of some waves are breaking.

Just to add interest, those waves are overtaking the boat and rolling towards the horizon in a determined fashion but up ahead we can see a wide expanse of calm water, which actually owes its presence to the tidal race.

In practice, for a wave to be really dangerous, it needs to be both big and breaking heavily.

Further Reading on wave patterns

Interaction of Water Waves and Currents , D H Peregrine

Prof. Howell Peregrine was a master of the subject of wave patterns and this 1976 paper is for maths enthusiasts. Available from libraries and some websites.

Coastal Turmoil: Winds, waves and tidal races by Ken Endean (Adlard Coles Nautical, £16.99). Explains the principles of wave patterns, but with hardly any maths.

Buy Coastal Turmoil: Winds, waves and tidal races at Amazon (UK)

Buy Coastal Turmoil: Winds, waves and tidal races at Amazon (US)

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Heavy weather sailing techniques

If you think you need to reef, you should have already reefed. reef early and reef often..

By Marcin Wojtyczka

Heavy weather sailing preparation and tactics.

With modern forecasting, a true storm will rarely arrive unannounced, but as you venture further offshore the chances of being caught out increase.

Heavy or bad weather is a situation in which navigation for both the boat and its crew is hard. However, there is no strict definition of which conditions heavy weather occurs. It depends on the wind and wave conditions, sailing area (coast upwind, leeward), type of boat and people on board. As an example, heavy weather for small boats could start already at force 6 or 7, for larger boats this might be 8 or 9.

Many sailors fear storms as the greatest danger on the water, even though more emergencies and fatalities occur during times of relative calm . Nonetheless, strong winds and high waves can wreak havoc on a sailboat and any sailor should know how to stay safe in heavy weather.

How to avoid heavy weather

In today’s world of satellite communication and more accurate weather forecasts, it is certainly easier to avoid heavy weather than before. Sailing up a sea storm is very hard, sometimes impossible. That is why it is important to plan, execute and monitor passages properly , with a good weather forecast in your hands and an alternative strategy in your mind.

You should generally stay in the harbour if bad weather is predicted. But once you are out on the sea, far from a harbour, and the forecast predicts a deep low in your vicinity, you might not have enough time to avoid the system. You can attempt to escape as far away from the low as possible, and ensure that you are some distance away from any shelving seabed which could increase the likelihood of breaking waves . Breaking seas present a risk to all yachts no matter how good their stability rating is. This is due to the rotational power of the waves. This also applies to a following sea with breaking waves. In this case, the yacht can be flipped over end to end (pitchpoled).

Other than that, you should plan passages to avoid unfavourable seasons, e.g. hurricane season that can create Tropical Revolving Storms (TRS) that must be avoided at all costs (North Atlantic and North Pacific: July - November; Bay of Bengal and Arabian Sea: June - November; South Pacific and South Indian Ocean: November - April).

Do not head out to sea if bad weather is predicted.

How to prepare for heavy weather

You should prepare the boat and the crew before the bad weather hits.

Assess your situation and make a plan for how you want to ride the storm. Can you afford to run 200 NM downwind? Are you on a lee shore? Are there any shallows? Will this area be prone to breaking waves? Two classic storm strategies are to try to keep away from land, so you are not blown up on shore, and to sail away from the storm’s path - especially its dangerous semicircle . If you are near a lee shore or shallows, you need to get away from it as fast as possible and work out a tactic that will keep you off until the sea state has calmed down. You should also try to get away from a high concentration of traffic and shipping lanes.

Once you are caught by the heavy weather you should try to minimize your exposure to potential breaking wave conditions by exercising prudent routing and sailing efficiently to minimize time at sea. If you are caught in breaking waves, you should minimize the chance of being caught beam-on (you need to orient the boat bow into the waves or stern to the waves).

Ports of refuge

Check if there is a suitable port which you can pull into to escape or avoid heavy weather conditions. In most situations, making landfall in strong offshore winds (blowing toward shore) should be avoided as it might put you and the yacht at risk. But a large, sheltered harbour might be approachable before it gets too bad.

Brief the crew

Inform the crew that harder conditions are expected but do not frighten anyone. Adjust the watch rota if needed. The crew should take seasickness tables, prepare warm clothes and stow their gear.

Clear everything on and below deck

Take everything below (including the dinghy) and stow it well. Make sure all running rigging is well stowed, so no lines are going to go overboard and foul the propeller. Make sure that all furling sails cannot unfurl by themselves (wrap sheets around the sail 3 or 4 times, cleat off the furling line, and secure the drum, so the sail cannot come unwrapped). Remove the bimini and deflate the dinghy. Ensure that all hatches and lockers are closed. Put away extra clothing, books and so on. Put away all dishes, pots, pans and so on. Leave nothing on the gimballed stove. Make sure all knives are in an enclosed drawer. Leave the stove gimballed, but if it can swing far enough to hit the safety bar in front of it, wrap the bar with a towel to protect the glass in the oven door.

Rest well, cook and eat a decent meal

Make sure that everyone is well rested, fed and watered and that you have some food prepared for the expected duration of the heavy weather (e.g. sandwiches, tea in a thermos). This is critical to prevent fatigue (especially if the crew is shorthanded) and be able to steer the boat relative to the waves throughout the storm.

Charge the batteries

You should have batteries charged in case you have to start the engine or use water pumps.

Double-check all safety gear

Ensure that the safety equipment is ready (EPIRB, PLB, PFDS and harness, VHF, Grab Bag , first aid kit etc.). This should generally be already checked as part of the passage prep, but it will not harm double-checking.

Reduce sails early and hoist storm sails (if you have one) whilst you still can, and certainly before dark. The force on a sail varies directly with air density and the square of the wind speed. Cold air is denser than warm air and so creates a greater force (could be up to 30% or so). It’s important to appreciate that wind force does not increase in direct proportion to the wind speed, but rather in proportion to the square of the wind speed. A 40kt wind has 4 times the force of a 20kt wind (since 40 40 is 4 times larger than 20 20). Therefore, it does not push on the boat 2 times harder; it pushes 4 times harder.

Prepare storm devices and hank on storm sails

Be ready to fly the storm sails. Put warps, drogue, sea anchor, chafe gear, or other devices for storm tactics on the top of the cockpit locker or on the cabin sole in a place where they can be easily reached.

Make the boat watertight

Secure all hatches and ports, and put hatchboards in. Check the main bilge pump and emergency pumps. Pump the bilge dry. Cover any air vents.

You can also find this video by Skip Novak very informative.

How to cope with heavy weather

There are several proven storm tactics, all of which aim to reduce the strain and motion by pointing one of the boat’s ends (either bow or stern) toward the waves. No one tactic will work best for all boats in all conditions, so you have to practice and work out a strategy that works best for you and your boat and be ready to implement a variety of tactics.

Don’t go especially if you expect breaking wave conditions

If conditions are wrong or are forecast to worsen, don’t go. If you can avoid the storm, then do so. Stay in the harbour and enjoy time with your shipmates. Make sure your anchor or mooring lines are secure, read a book or brush up on some sailing knowledge with your crew (e.g. COLREGs, navigation).

If your boat is threatened by a hurricane, strip all excess gear from the deck, double up or redouble all docking or mooring lines, protect those lines from chafing, and get off. Do not risk your life to save your boat.

Head for safe harbour

When the heavy weather begins or is predicted, the first impulse is often to drop the sails, start up the motor and head for land. If you can safely reach a harbour, this may be your safest option. The danger lies in being caught in the storm, close to shore, with no room to manoeuvre or run off. The wind and waves can rapidly turn shallow areas or narrow channels into a more dangerous place than open water, especially if the storm will be short-lived, and it’s mostly a matter of waiting it out. Waves become steeper and more likely to break in shallow areas, making it difficult to control the boat. Also, consider the risks if your engine were to die and the wind rapidly blow you onto the shore. You may have better options staying in open water and riding out the storm.

Keep the bow or stern oriented toward the seas

In heavy weather, the most common reason for a capsize is a breaking wave on the beam. Don’t beam reach when wave heights equal or exceed the beam of the boat and don’t lie beam-to the seas in breaking waves. Try to balance the boat for the wind angle you want to maintain, e.g. use mainsail for going to windward, and headsail when running off.

Steer downwind course (running off)

Active steering downwind course is probably the best technique for a modern lightweight boat as long as you have plenty of sea room and a competent helmsman. If the stern is not kept perpendicular to approaching waves, a wave can push the stern around to one side, causing a broach and capsize.

Advantages of running off:

• Reduction in apparent wind speed eases the strain on the boat’s equipment
• Steerageway is maintained, so the helmsman can avoid a particularly bad wave
• If the crew is not able to steer manually the boat is likely to manage on her own with autopilot able to handle the steering as long as the waves are not breaking

Disadvantages of running off:

• Lots of strain on the boat. Big ships and long keel boats like fisherman boats prefer to take big waves on the bow, but there are serious forces in play and modern lightweight performance yachts are better off going with the wind and waves rather than fighting against the nature
• The yacht might pitchpole as it accelerates down the waves and hit the waves in front. Streaming warps or a drogue with bridle might be necessary
• Useful if it sends you in the right direction, but perhaps not very good if it puts you far from your destination
• You will also stay in bad weather for longer, rather than letting it pass over you
• Having someone on deck helming puts them in a vulnerable position with potential waves landing on the deck
• Need a lot of sea room. Most depressions are fast-moving and usually wind down after 1-2 days. With an average boat speed of 5 knots, you will need a minimum of 120 nautical miles of sea room

When surfing the waves at some point you might have to slow the boat down to be able to control it. The sail plan would mainly depend on your boat and available sails on board. For a typical cruiser, this could mean a main sail with a second or third reef and reduced headsail (rolled or storm jib). You can also drop the main sail or use a fourth reef .

When running it is necessary to keep the yacht at right angles to the seas. Therefore, it is advantageous to set the sails as far ahead as possible and to take off the main thus improving the capability of steering because the distance between “centre of effort of the sails” and “centre of effort of the rudder” is enlarged.

In extreme cases, where even a scrap of a sail is too much, you may need to drop all the sails and simply run under bare poles. In true storm conditions, the resistance of the mast, hull, and rigging will drive most boats at 4 to 5 knots. A staysail sheeted flat amidships can help keep the boat tracking downwind.

Be wary though that if you run free and the boat starts surfing regularly, you may be knockdown. In the Queen’s Birthday Storm, three boats ran free. One was rolled and dismasted, one was knocked down past 90 degrees and dismasted, and the third deployed a speed-limiting drogue off the stern and was fine. Some sort of drag device can help keep the boat upright in survival storms. Drag devices can slow the boat down and orient its bow or stern into the waves reducing the chances of getting knocked down and rolled. That being said, some very experienced sailors have found that the boat did better when they got rid of the drogues they were towing and ran free. In the classical text passage, this is how Bernhard Moitessier described it: “Now she is running bare poles, free, heeling, when the sea is running up at an angle of 15 to 20 degrees, is accelerating like a surfer … and is responding to the helm when I bring her back downwind”.

Beat possibly by the assistance of the engine

If you lose too much ground to leeward you can try to beat to windward with a reefed mainsail and the engine. Relying on the engine in an offshore storm will probably not be sustainable in the long run because of:

• fuel limitations
• stress on the engine itself from operating at extreme angles of the heel (engine not lubricating correctly and overheating)
• rough seas can stir debris in the fuel tank, clogging fuel filters, and stopping the engine at a potentially very unsuitable time
• in a following sea, water can back-fill the exhaust and flood the engine if the exhaust is not high enough.
• accidental flooding can also occur if the engine cooling water anit-syphon becomes blocked

Nevertheless, this remains a viable option in coastal conditions when dealing with a passing squall.

Heave-to (if your boat can, practically suitable only for traditional voyagers)

Heave-to under reduced sails with a staysail or jib sheeted to windward and the helm lashed over to maintain a heading of approximately 45 degrees off the wind.

Heaving-to gives the crew a rest, and it can be a safer means of riding out a storm rather than trying to sail it out, but you need the right boat for this (see below). It is a classic survival technique where you tack the boat through the wind, leaving the sails backed, and the wheel lashed to windward. Locking the rudder with a stretchy line is the best because it holds but also gives slightly to avoid extreme tension. Note that in a strong wind, it might be dangerous or impossible to tack the boat, so you should rather back the headsail to windward by trimming the windward sheet.

Heaving-to stabilizes the boat and slows down the drift to 2-3 knots on average. The leeway a boat makes while hove-to means that you need a sea room. In offshore gale conditions, most boats will drift 20-50 miles to leeward every 24 hours.

You should be able to adjust the sails to sit at about 45-60 degrees off the wind. Finding the right balance­ where a boat will sit comfortably at the correct angle to the wind and not give up too much ground to leeward will require some adjustments. You should lower or deeply reef the main or raise a storm trysail (very small storm mainsail) as well as a small headsail (storm jib) to reduce loads on the rig. Depending on how the boat is pointing to the wind and waves you might need to drop the headsail or the mainsail.

A really cool part of heaving-to is that the boat will leave a wake to windward. Breaking waves hit this “slick” and flatten out, thus reducing the wave action on the vessel.

Modern boats generally do not heave-to very well, and certainly not as well as a solidly built full-keel boat will. The sail plan and hull geometries of modern designs just do not let the boats lie stable to the wind. You need to experiment with your boat and see how the boat behaves. This tactic will be effective in moderate seas. The danger arises when the swell picks up and starts to break. This might leave the yacht beam onto the prevailing seas.

• Back the headsail to windward by trimming the windward sheet. If you have a big headsail, roll it up to handkerchief size or set up a storm jib. Do not gybe because the boat might fly down a wave and tacking might be impossible
• Reef and ease the mainsail until the boat stops all forward motion
• Put your rudder over hard to windward, taking care that the boat does not go head to wind. Lash the helm well, so it can’t work
• Play with the mainsail trim until a balance is struck at a good angle to wind and waves. The ride should be comfortable. It’s all about a balance between what is below the waterline (keel and rudder) and windage above (sails and rig)
• If there is still too much tendency to climb to windward, drop the mainsail. This would probably be the case if you had a third reef, which would be too much sail. A fourth reef (storm trysail size) might work
• Keep a close eye on the boat for some time to make sure it stays in balance during various cycles of wave and swell patterns
• Crew can go below. One watchkeeper is sufficient, booted and suited to go on deck to make any changes

Heave-to earlier rather than later. It is much easier to set up everything in a controlled situation. If the wind is rising, there is no point waiting as you will not lose much distance anyway.

Another technique akin to heaving-to is forereaching. Forereaching essentially keeps a boat moving forward to windward (off the wind at 45 to 60 degrees) at greatly reduced speed and is accomplished by sheeting the jib amidships (not quite backed) or lowering it all together, with the reefed mainsail sheeted in tight and the helm lashed slightly to leeward with stretchy line. Think of it as sailing your boat very inefficiently to windward. Often a boat that is improperly hove-to ends up forereaching unintentionally. Most boats will foreach comfortably into gale-force winds under a double-reefed mainsail. A triple-reefed mainsail or trysail will keep the boat pointed into the wind and moving forward on sloops. A staysail may work better on a cutter.

Forereaching can be a better alternative to heaving-to in certain situations. In tidal areas, for example, forereaching can be used to slow down a boat without losing ground to an outgoing tide or current. Forereaching allows you to continue to make slow miles toward your destination without beating up the boat and yourself. If you are just trying to slow down the boat and cannot afford to make leeway, forereaching makes a lot of sense.

Forereaching is a perfectly acceptable storm tactic as long as the waves are not breaking or dangerously confused. This is because large breaking waves will try to push the bow off and expose the side of the boat to the sea. If the boat is becalmed in the trough, it will fall off the wind before the next wave arrives and could get it beam-on. Because of the slow boat speed, you might not be able to head up fast enough. In a dangerously confused sea, a wave may strike the opposite side and force the boat to tack through. She might also tack inadvertently if the wind increases enough to overpower the rudder and bring her head through the wind. From down below you should be able to assess and tell if you are reaching the limits of forereaching as a storm tactic if the boat tacks or if waves are knocking the bow off repeatedly and interrupting the windward motion.

To effectively and safely forereach in storm conditions you need a boat prepared for offshore sailing. Your boat needs to be able to take waves on the bow and lots of loads. Sturdy boats with long keels will be better for taking big waves on the bow than modern lightweight performance yachts which are generally better off going with the wind and waves.

Lay a drogue astern

Even if running under bare poles you have too much speed, there are several possibilities to decrease the speed to avoid pitch poling or broaching, e.g. using warps (bight of the line will trail behind the boat 300 feet or so), a chain with anchor, or deploying a drogue. You should practice using drogue before in various conditions. These are difficult-to-handle devices and the load generated by them is enormous. Theoretically, speed-limiting drogues should be deployed two waves back to keep it from being jerked out of the face of the wave as the boat accelerates toward the trough. But once you deploy it, the tensions will likely be too big for you to be able to adjust anything.

Studies over the last years have shown that drag devices help stabilize a boat in survival conditions. Waves tend to be steep and break early in the storm. This is because the underlying water is not yet moving at speed with the wind. During that period, drogues or towing other objects like warps stabilize the boat. After the storm winds have been blowing for 48 hours or more, the waves become less steep, but their velocity increases considerably. Drag devices may then slow the boat too much in front of the fast-moving waves. Cutting the drag devices away may allow the boat to rise up and go over the waves more smoothly, but only if the boat is hand steered to avoid breaking seas. This situation is most likely to occur in the Southern Ocean where fully developed seas are more frequent.

If you do plan to use a drogue, deploy it before the bad weather hits. Amongst drogues the Jordan Series Drogue receives a lot of praise from long-distance sailors. A more conventional and solid drogue should do it as well (e.g. Seabrake Drogue ).

If things get very bad, the last resort might be lying ahull: drop all the sails, fix the tiller to leeward and lock oneself inside the boat, allowing the boat to drift, completely at the mercy of the storm. The ride will not be comfortable, and the boat may not make it, but it is an option when there are no others left. This technique is best suited to heavy displacement yachts with excellent stability characteristics. Light, modern boats will often lie abeam big seas which are very prone to roll. Damage to the boat is likely. Of the three boats that lay ahull during the infamous Queen’s Birthday Storm, only one, a catamaran, remained upright. The other two were both rolled and dismasted.

Many experienced ocean sailors are of the belief that once it has got into severe gale conditions the crew should all be below deck, with the boat potentially sitting to a drogue or sea anchor from the bow and the hatches battened down. Indeed, many of the injuries sustained during the 1979 Fastnet race were from people trying to helm or move around the boat.

Drop an anchor

If you have in the vicinity of a shallow water, and you have no other option to escape the lee shore you can drop an anchor as a last resort. Requirement: 30 - 50 m of chain, plus nylon cable of the same length (or both longer). A cable of nylon is elastic, and it is able to absorb the movements back and forth.

My roadmap for cruising on a modern performance boat

Up to Beaufort 4

• Maintain the course
• I reef in the main (or rolled-in)
• 2nd reef in the main (or rolled-in)
• Reduced headsail

Beaufort 7 and up to a wave height which roughly matches the beam of the ship

• 2nd or 3rd reef in the main (or rolled-in)
• Running: further reduced headsail
• Upwind course: storm jib
• Important not to sail beam-on to the seas especially if the sea is confused or breaking, switch to running (vessel oriented with the stern into the waves) or to beating (with the bow into the waves)
• Using the self-steering as long as possible with somebody near the helm, who takes the wheel if necessary or forereaching with a wheel lashed with a stretchy line
• 3rd reef in the main (or rolled-in)
• with additional support from the engine if needed
• main with 3rd reef (or rolled-in) and storm jib
• or storm jib only to avoid broaching

Upwind course

• main only, 3rd reef (or rolled-in) or storm trysail
• steering manually or forereaching
• as long as the sea permits
• under storm jib solely

Beaufort 10 and more

• Running under small storm jib only or bare pole
• Maybe with a drogue or towing warps to reduce speed and keep the stern held down
• Retreat of the crew into the ship, close off the vessel
• Reporting the position on VHF if near a busy area: “Restricted in manoeuvrability”
• Stay with the boat as long as the boat floats

Golden rules of heavy-weather

• If you can, don’t go if heavy-weather is predicted.
• Keep clear of any potential lee shore.
• Avoid areas prone to breaking waves (e.g. shallowing shore, sea mounts, harbour bars on ebb and swell, headlands).
• Prepare the boat and crew before the heavy-weather hits.
• Don’t beam reach when wave heights equal or exceed the beam of the boat, especially in breaking sea.
• Reef early. Don’t be caught over-canvassed.
• Balance the sail plan for the wind angle you want to maintain.
• Don’t leave the boat until the boat leaves you.
• Get underway once conditions moderate.
• There is no one right way of handling storm at sea. There is only what works for different boats and their captains in different storms.
• Don’t lie ahull in a monohull unless there are no other options left. This tactic is most likely to result in knockdowns, rolls, and dismasting.
• Running free is likely to result in a knockdown in survival conditions when the boat starts surfing regularly.
• Some sort of drag device (e.g. drogue, warps, anchor) can help keep the boat a survival storm by making sure the boat is oriented with the bow or stern into the seas.
• Having-to does not seem like a successful strategy for modern performance boats.
• There is no “silver bullet”. Keep trying different tactics until the boat feels “right” in the given conditions.
• Keep the relevant amount of sail area for the conditions. Carrying too little sail means the boat will be sluggish and unresponsive allowing her to end up beam-to the seas. You will also stay longer in the storm.
• Get underway once conditions moderate. Most knockdowns and capsizes happen near the end of a storm, after the wind has shifted causing the waves to become more confused. Getting some sail back up at the end of a storm is the best way to stabilize the boat and deal with the dangerous sea state.
• If the boat speed drops to 50% of the hull speed, the boat is under-canvased and needs more sail area to drive through the waves, even if that means sailing at a higher angle of the heel than normal. Hull speed in knots equals 1.34 times the square root of the waterline length in feet.
• Don’t leave the boat until the boat leaves you. It has been well documented in sailing disasters such as the 1979 Fastnet, the 1998 Sydney-to-Hobart Race, and the 1994 South Pacific Queen’s Birthday Storm that you should not abandon a vessel until it is literally sinking beneath your feet, and you have to step up off the deck to your raft. The boat is the safest place to be almost all the time, and staying with it increases your chances of survival. Case after case, crews have been injured or killed in a liferaft, while their abandoned vessels have been found weeks later floating happily on their own.
• Clip on the harness whenever the conditions deteriorate, or you feel uncomfortable.
• When climbing to the crest of an unusually large, steep wave, head up and then bear away to slide down the boat at an angle of 60-70 degrees to the wave to keep the boat from free-falling or burying its bow in the trough. A similar approach can be used when running off

You and the storm

Few people get to experience the full fury of a storm. Although everyone will remember it differently years later, a long, wet, cold sail through a storm can be miserable. It is memorable but not pleasant so do not dream about it. As a skipper, keep calm and make the best of it. Watch over your crew, offer help to those who need it, and speak a few words of encouragement like “This is miserable, but it will end”.

Additional resources

• Skip Novak's storm sailing techniques.
• Essential boathandling skills in heavy weather.
• Using a drogue.

Happy Sailing!

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Dangerous waves and your boat

At what size  do waves get big enough to cause real trouble for your boat?

by Steve Tredup

It’s dark. It’s storming. The waves, when you can see them, look large. And you are sailing a long way from land. One of the greatest concerns a sailor may have is that he or she will be caught in a situation where his boat may be knocked down or rolled by a wave.

Despite being frightened by stories about exceptionally dangerous storms, such as those that wreaked havoc on the 1979 Fastnet or 1998 Sydney to Hobart races, not all storms create dangerous breaking waves. But some storms do and a prudent sailor has to ask: Do I know what wave heights are dangerous to my boat? Do I know when breaking waves can occur? Do I know when these conditions might occur where I am sailing?

This is not about heavy weather sailing techniques, but knowing which waves caused by heavy weather may be dangerous.

Roll, roll, roll, your boat When is your boat in danger of being knocked down or rolled by a wave? A study conducted by the University of Southampton’s Department of Ship Science and a similar study by the Society of Naval Architects and Marine Engineers (SNAME) along with the United States Yacht Racing Union (now US Sailing) have shown that three conditions usually have to exist:

1. Wave height must exceed a certain percentage of the boat’s length. At this point the wave becomes dangerous and contains enough energy to overcome a boat’s righting moment.

2. The boat is broadside or oblique to the wave. The more a boat moves from being perpendicular to a wave, the greater the chance of a knock down. If the boat is bow or stern onto the wave, the chances of being rolled are greatly reduced. Yes, a boat can be pitch-poled (tossed end-over-end), but the size of the wave needed to do this greatly exceeds the size of the smaller wave needed to knock a boat down when broadside to a wave.

3. The boat is struck by a breaking wave. Unless the wave is breaking, the boat should ride up and over the wave regardless of the wave height in comparison to the boat length and the boat’s orientation to the wave. That is not to say that it will be comfortable or possibly cause the boat to go out of control. But without the wave breaking on the boat, the boat itself should not be knocked down.

An ocean wave is energy. Along with the speed of the wave, the larger the wave is, the more energy it will contain. Therefore, the wave has to be of a certain height in order to have enough energy to roll a boat of a certain length and displacement.

Most sailors would be surprised at the minimal wave height needed to roll a boat. Andrew Claughton (who co-authored the University of Southampton, Department of Ship Science’s report) writes in Adlard Coles’ Heavy Weather Sailing by Peter Bruce, “During the model tests that were carried out to investigate the problem, when the breaking wave was 30 percent of the hull length high, from trough to crest, it could capsize some yachts, while waves to a height of 60 percent of the hull length comfortably overwhelm all of the boats we tested.” So, the starting point for a wave to be dangerous to rolling a boat is one that is only 30 percent high as the boat is long.

In order to be rolled, a boat’s righting moment has to be overcome. Obviously, different boats will be more susceptible to rolling than others based on length, beam, displacement, roll inertia, and center of gravity. A monohull’s resistance to heeling is created by its centers of gravity and buoyancy. This resistance to heeling is called a boat’s righting moment, which is created by the horizontal distance from the boat’s center of gravity and the center of buoyancy as the boat tilts. The farther apart horizontally these points are, the more righting moment the boat has.

As a boat tilts farther over, it will eventually reach its maximum righting moment when the maximum horizontal distance between the centers of gravity and buoyancy is reached. If the boat tilts over more, the boat still has a positive righting moment but it will be decreasing. It will continue to decrease until the center of gravity and the center of buoyancy line up again, but the wrong way, which is known as the angle of vanishing stability (often beyond 90 degrees). The boat could then fall either way, but once the point of vanishing stability is passed, the boat will continue over until a new equilibrium is found, which could be a complete roll or an inverted position.

The wave will have to be breaking along its crest as it encounters the boat to roll the boat. At this point, the boat will be at the top of the wave face and will be tilted over by the steepness of the wave. When the breaking front of the wave hits the boat, it acts like a power force to throw the boat over, down the wave into the trough. How far the boat is knocked down depends on the energy of the wave and the righting moment of the boat.

Your boat may be more or less susceptible to rolling than other boats based on its design, but the aspects to remember are that although your boat may be severly tilted over by the wave front, the wave will have to be over 30 percent of the boat’s length, be breaking on the boat, and the boat will have to be orientated obliquely (beam on is the worse) to the wave to knock the boat down or completely roll the boat over. Unless the wave is so large that it pitch-poles the boat, a boat that is bow or stern onto the wave should not be rolled.

Wave background Local wind causes waves and as these waves get separated out of a localized wind, it is called swell. Swell from outside an area and local wind waves often interact. When a crest meets another crest, the result is the combined height of both. For example, the crest of a five-foot swell and the crest of four-foot wave would stack, resulting in a nine-foot wave (for a wave to double like this, it requires that both waves have very long and regular swells). However, if the crest meets a trough, then they cancel. In our example, this would result in a one-foot wave. All ranges in between will also be encountered.

Because of these interactions, waves will appear different from one another and may seem confused. Waves will appear across a large spectrum of sizes, although to a local observer, there will appear to be a general height. This is why wave forecasts, such as from the National Oceanic and Atmospheric Association, give a range, such as six to eight feet, covering a broad area (called a wave field).

This range, though, is often misunderstood. First, the wave height given is the significant wave height, which is the average of the highest one-third of the waves that may be encountered. It is not the average of all waves, nor will all waves be in this range. Some waves will be smaller and some waves will be higher. In fact, you can expect to see a wave almost twice as high (!) as the significant wave height. This type of wave is rare, however, only showing up once every 3,000 waves.

Wave lesson Predicting dangerous breaking waves is complex. The best information that most sailors will have to rely on is the weather report. Therefore, when you are sailing, the wave forecast portion of the weather report is just as important as the rest of the report. The wave height (from bottom of the trough to the top of the crest) and the wave length (the distance from one crest to the next crest or one trough to the next trough) are the two pieces of critical information. Once you know the wave height and length, you can determine whether the waves will have the potential to be breaking or not in deep water.

A wave will collapse, or break, in deep water depending on the wave’s steepness.  The base of the wave (trough to trough, i.e., the wave’s length) can only support a wave of a certain height. If it exceeds that height, the wave becomes too steep and it collapses and breaks forward.

There are some varying estimates of the scientific, precise moment when the wave will collapse, but generally, when the wave height exceeds the wave length at a 1:7 ratio, it may begin to collapse. This is called the wave’s breaking point, but I call it the “Rule of 7 or Less,” if the wave length is 7 times or less than the wave height, then the wave may break. This is true for any measurement type, feet or meters. For example, if the wave height is 15 feet, multiplying that by 7 will give a minimum wave length of 105 feet. If the wave length is 105 feet or less, then the wave has the potential to be breaking.

Is there danger? To know if you have entered a wave-height danger zone, you must first know what wave height is dangerous to your boat. Remember, a wave will have enough potential energy to knock your boat down starting at 30 percent of its length and certainly will be large enough if it is 60 percent of the boat’s length.

Using the weather forecast or manual prediction, you need to know the wave heights and lengths you will be expecting to encounter over the next day or so. Will the wave heights exceed your danger zone? Could another condition, such as more wind or a contrary current, suddenly make normally safe waves dangerous?

If yes, then you need to know if the waves will be breaking. If the wave length is 7 times or less than the wave’s height, then you should take precautions.

For example, using the minimum 30 percent wave height to boat length, if your boat is 40 feet long, then the wave-height danger zone starts at waves 12 feet high (40 x 30). A wave 12 feet high could knock down a boat 40 feet long if the boat is caught somewhere near beam onto the wave as it breaks. Following the Rule of 7 or Less, you know that a 12-foot wave could break only if the wave length is less than 84 feet (12 x 7).

In contrast, these conditions should not present a danger to a 40-foot boat even though some may find the below conditions worrisome.

If the wave is higher than 12 feet, but is not breaking (a non-breaking wave cannot throw the boat down into the trough); If the 12-foot-high wave’s length exceeds 84 feet (the wave will not be breaking); or If the wave is breaking, but the wave height is less than 12 feet (too small to overcome the boat’s righting moment).

To determine dangerous wave heights and lengths for your boat, you can use these formulas:

Danger Wave Height W Height = B Length x 30%

Danger Wave Length W Length < = W Height x 7

However, to make it easier, the accompanying chart (pg. 47) is designed for boats 30 to 60 feet based on a dangerous wave height of 30 percent of the boat’s length.

Knowing the wave conditions that may be a danger to rolling your boat will allow you to take action to avoid or prevent it.

Steve Tredup is a sailor who works in the insurance industry. Tredup lives near Chicago and sails on Lake Michigan.

By Ocean Navigator

Enjoy the Beautiful Waters

Staniel cay & black point // exuma cays // bahamas.

At Breaking Waves Boat Rentals we guarantee that we’ll make you happy. Our boats are ready to take you and your family exploring, sightseeing, fishing and snorkeling, in the most beautiful waters of the Bahamas.

We offer full-day and half-day tours near Staniel Cay, Black Point and surrounding areas in the Bahamas’ Exuma Cays. You can rent a boat with a guide or you can take the boat out on your own. Our guides know all the best spots and are a joy to have along for the ride.

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Our fleet of boats are all professionally maintained and equipped with VHF radios, life vests, coolers, and GPS. We have snorkel gear for adults and kids to rent. Drop off and pick up service is available to Staniel Cay, Black Point and surrounding areas.

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The following activities are available near staniel cay and black point:.

• Catch a Wide Variety of Fish
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Sailboat Stability Uncensored

The merits and limitations of the calculated gz curve..

At its most basic level, my goal as a sailor is pretty simple: keep my neck above water. Speed, comfort, progress toward a destination are nice, but if I need gills to achieve any of these, something is amiss. And since an upside-down boat tends to interfere with this modest ambition, I’d say our recent obsession with stability is justified.

This is far from our first foray into this topic. Shortly after the 1979 Fastnet race disaster , in which 15 sailors died, Practical Sailor embarked on a series of articles on sailboat stability. The racing rules of that era had resulted in designs that were quicker to capsize than their heavier, more conservatively proportioned predecessors, and we needed to explore why.

Since then, the lessons of Fastnet have been absorbed by the design community, culminating with the CE Category system and formulas used by various racing bodies like the Offshore Racing Congress to evaluate a boat’s fitness for the body of water where it will sail. But it’s clear that the tools we use to measure stability, and the standards we’ve established to prevent future incidents are still imperfect instruments, as we saw in the fatal WingNuts capsize in 2011 . And in the cruising community, where fully equipped ocean going boats hardly resemble the lightly loaded models used to calculate stability ratings, we worry that the picture of stability is again becoming blurred by design trends. This video gives some insight into the dockside measurement process for racing boats.

Last month, we examined multihull stability , including an analysis of several well publicized capsizes. One of the key takeaways from that report was the significant impact that hull shape and design can have on a multihull’s ability to stay upright. Another key observation was the distinction between trimarans and cats, and why lumping them together in a discussion of stability can lead to wrong conclusions. As we pointed out, many of the factors that determine a multihull’s ability are related to hull features—like wave-piercing bows—that are difficult to account for when we try to calculate stability.

This month, we take another look at monohull stability. This time it’s a formula-heavy attempt to tackle the conundrum that many cruising sailors face: How can I know if the recorded stability rating for my boat reflects the reality of my own boat? Or, if there is no stability rating from any of the databases, like the one at US Sailing, how do I assess my boat’s stability?

Stability Resources

If you are unfamiliar with this topic, I’d recommend reading three of our previous reports before digging into this month’s article. “ Dissecting the Art of Staying Upright ” and “ Breaking Down Performance ,” both by PS editor-at-large and safety expert Ralph Naranjo, take a broad view of sailboat design elements and how they applies to contemporary sailors. Nick Nicholson an America’s Cup admeasurer and former PS Editor, also offers a succinct discussion of stability in his article, “ In Search of Stability ,” which I recently resurrected from the archives. (Nick, by the way, is no relation to the current editor.)

When we’re talking about stability, the essential bit of information that every sailor should be familiar with is the GZ curve. This graphic illustration of stability highlights the boat’s maximum righting arm, the angle of heel at which resistance to capsize is greatest. It also illustrates the angle of vanishing stability (also called the limit of positive stability), the point at which the boat is just as likely to turn turtle as it is to return upright. Most boats built after 1998 have a GZ curve on file somewhere, and US Sailing keeps a database of hundreds of boats for members. As this month’s article points out, however, the published GZ curve does not always perfectly transfer to our own boats. Nevertheless, it is usually a good benchmark for assessing your boat’s stability ratio—not to be confused with capsize ratio the stability index or STIX .

For a succinct discussion of stability ratios (see below), Ocean Navigator’s excerpt from Nigel Calder’s Cruising Handbook lays good groundwork for the theory. If you really want to dive into the topic, Charlie Doane presents a good overview in this excerpt from his excellent book “ Modern Cruising Design .” Doane, like many marine journalists, relies greatly on the work of Dave Gerr , former director of the Westlawn Institute of Yacht Design and now a professor with SUNY Maritime Institute. Gerr’s four books “ Propeller Handbook ,” “ The Nature of Boats ,” “The Elements of Boat Strength,” and “Boat Mechanical Systems Handbook,” all published by McGraw Hill, illustrate Gerr’s rare talent for taking complicated topics and making them comprehensible and fun to read.

The GZ Curve

Shaped like an “S” on it’s side, the GZ curve illustrates righting lever. The high peak represents a boat’s maximum righting arm (maxRA), the point at which the forces keeping the boat upright (ballast, buoyancy) are strongest. The lowest valley, which dips into negative territory, represents the minimum righting arm (minRA), the point at which these forces are weakest. The curve also clearly delineates the limit of positive stability (LPS, also called the angle of vanishing stability), where the curve crosses into negative territory. Generally speaking, an offshore sailboat should have an LPS of 120 degrees or more. As Naranjo puts it, “It is this ability to recover from a deep capsize that’s like money in the bank to every offshore passagemaker.”

• Notice how lowering ballast lowers the center of gravity (CG) and increases a vessel’s limit of positive stability. In these examples, three identical 30 footers with the same amount of ballast, but differing keel stub depths, alter their draft and GZ curves. Boat 1 (5’ draft), Boat 2 (6’ draft) and Boat 3 (4’ draft). Note that Boat 3, the shoal draft option, has the lowest LPS and Boat 2, has the deepest draft, highest LPS and will sail to windward better than the other two boats. Editor’s note: One would think that with all the reporting we’ve done on stability, we’d be able to label a GZ curve correctly, but in the print version of the March 2021 issue we have mislabeled the curve. I apologize for the error. Sometimes, despite our best efforts, our own GZ curve turns turtle during deadline week. The correct version of the curve appears in the online issue and in the downloadable PDF. If you have questions or comments on boat stability, please feel free to contact me by email a [email protected], or feel free to comment below.

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17 comments.

Thanks for this reminder, another error has crept into the diagrams I think. The yacht seems to have 2 CBs and no GG.

I noticed that also, Halam. With no center of gravity and all buoyancy that boat will never sink. Of course, it could be at rest upside down also.

The link to the US Sailing database is pointing to a different place than I think you intended. It is not the database of boats, but rather information on curve calculation and definitions.

Hi Darrell, sorry to be the bearer of a correction, but it looks like the CG is labeled as CB in the first graphic.

As far as I know, a rule of thumb is that a sail boat can tolerate cross breaking waves not higher than her max beam. Is it true?

It often amuses me to see the many crew sitting out on the gunwale of a keel boat, (monohull) as the righting effect must shorely be minimal. Especially when compared to a small racing trimaran. It does help the ‘Gyration’ as shown in the Fastnet tragedy. Even the ‘Skiffs’ have ‘racks’ out the side, & I’ve seen all sorts of ‘keel arrangements’. They just haven’t put ‘floats’ on the end yet. I’d love to see someone do a ‘stability kidney’, as Lock Crowther said (all those years ago), the the righting, (capsizing force is 35? degrees off the bow. Thought provoking? not antaganistic. Keep up the good work, and thanks ‘B J’.

A useful view of stability is to consider where the energy to resist capsize is stored. As a boat rolls, the center of gravity is also raised with respect to the center of buoyancy, so the weight of the boat is lifted, at least through some angle (as long as the GZ is positive) and energy is stored as a lifted weight. This means that a stability incident is exactly equivalent to rolling a ball up a hill; it will always roll back down until it passes over the top of the hill. This is why most commercial and military stability standards use “righting energy” for at least one criteria. The ISO 12217-1 standard for coastwise and oceangoing power boats requires at least a minimum absolute energy and an energy ratio exceeding a nominal overturning energy of combined wind and wave (similar to the IMO standards for cargo ships and 46 CFR 28.500 for fishing vessels).

Can anyone comment on the stability of Volvo Ocean Race boats? While various mishaps have occurred over the years, I don’t believe any of them have capsized and remained inverted. VOR boats are nothing like the Pacific Seacraft and similar designs from more than 50 years ago, yet they seem “safe”.

Does anyone know why? Size, keel depth and weight, modern design tools?

Good and useful article, particularly to someone considering buying a new or used sailboat. As an add-on to the effect of draft, I would add that most, if not all, builders increase the weight of the keel to try to compensate for the reduction of righting moment with the reduction in draft. I recommend to readers Roger Marshall’s outstanding book entitled “The Complete Guide to Choosing a Cruising Sailboat”. Chapter 3 “Seaworthiness” and chapter 10 “Putting it All Together” are worth the cost of the book many times over. Unfortunately the book is getting out of date, it was published in 1999 and many newer sailboats have come on the market.

Mark, thank you for recommending to read Roger Marshall’s book.

May i suggest reading the book, “Seaworthiness the forgotten Factor”. The author (C.J.Marchaj) makes a number of interesting observations about modern boat design (published in ’86, so not that modern). What sticks with me is the notion that one aspect of seaworthiness is how well a person can survive inside the boat in question– deeper keels make for more righting moment but also a snappy roll, for example, promoting incapacitating seasickness. The boat has to be well enough behaved to “look after” the crew.

My boat 40 ft Samson SeaFarer ketch is fairly tender initially but then settles down once the rail is int he water….but I have never had the top of the mast in the water to see if it would recover well. Since I am not and engineer or math whiz (and don’t want to be!) I wonder if there is a practical way to actually test the stability while on the water. Is there a way for example to pull the top of the mast down to varying degrees/angles and measure the force it takes to do it and use that as a guide to stability. Could that provide some extrapolative certainty to going further around the wheel of misfortune? Crossing between NZ and Australia (45 years ago..) we were knocked over (not my current boat) with the top third of the mast in the water and she righted very quickly (very comforting) – no great mishap except to make the cook go wash the soup out of his hair and confirm all the things we hadn’t tied down…including dishevelled crew.

Cheers Gerry

Can someone please link to the article referenced above on multihull stability? I’ve searched, but cannot find it. Thank you kindly!

I have the same inquiry as Jet. I can’t find the Multihull article. Please advise ASAP!

The link in the 4th paragraph works for me:

https://www.practical-sailor.com/sailboat-reviews/multihull-capsize-risk-check

Couldn’t find this link either. Thanks.

Is it possible to get a link to the USSailing boat database, or some hints on where to find it on the site? The current link just goes to ussailing.org.

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51’ Wasa Sailing Sloop Grounded Near Ocracoke Inlet Early On The Morning Of November 2nd

The First Shipwreck of 2023

Each year, the tough weather conditions and shifting shoals of the Outer Banks claim several victims, especially in fall, winter, and early spring. This season, the shipwrecks begin with the 51′ Wasa Racing Sloop grounded near the inlet beach of Ocracoke in the wee hours of the morning on November-2. The vessel was motoring southbound to Florida on the oceanside of the Cape Hatteras and Ocracoke when they ran aground near Ocracoke Inlet after experiencing electrical and mechanical failures aboard. The crew survived with no injuries, but the vessel is quickly becoming a total loss. It took less than 24-hours for the boat to become fully covered in sand and totally under the water. Salvage attempts were abandoned when the weather became tougher than originally forecasted. Now, only the beautiful mast and spreaders can be seen sticking just above the waves as if this happened weeks or months ago. Unfortunately, the situation that led to this wreck is not unique and seems to repeat itself every year because of the geography of Cape Hatteras, Cape Lookout, and Cape Fear. The three capes rub very closely with the strong and warm northward flowing Gulf Stream, the lesser Labrador Current, and the resulting eddies that spin off of both. Many seem to underestimate the strength of the wind and the state of the sea, and the result is often a near miss or a complete catastrophe.

The grounded 1983 WASA Atlantic 51 Sloop is a nicely appointed sailing sloop. It is a high performance racer-cruiser built in Sweden with a 7’ draft. The mast boasts 3 spreaders topped with a jumper strut set of spreaders near the top. While sailing, this rod rigging supported mast is additionally supported by running backstays which appear to be check stays intended to keep the center of the mast from bowing forward as the boat pounds into waves. Some compare the hull shape to that of a Santa Cruz 50 but built with heavier fiberglass composites.

Causes of the Wreck

Shipwrecks normally result from a series of unfortunate errors and equipment failures compounded by darkness, cold, high winds, and breaking waves, and this wreck is no exception. A cold front with high winds and squalls was passing through the area that night. Ultimately, the cause of this wreck is a snowball of mishaps. Boat parts and equipment are most stressed in bad weather and high sea states so they tend to fail when you need them most. The owner and primary captain reports a failed alternator which caused battery failure and the resulting loss of electrical systems and navigation tools. As a result, at the time of the grounding, the captain was down below attempting to troubleshoot electrical failures when the watch crew navigated off course into Ocracoke inlet, close to the beach, and hard aground.

Weather, Sea Conditions, and Equipment Failure

The weather on the night of the accident was really bad, but typical for the Outer Banks during the fall, winter, and spring. The pattern is well established and well predicted. Rapidly passing cold fronts regularly push through the area and become amplified by the warm Gulf Stream.  These fronts can come through as frequently as twice per week in the winter. The cycle begins with increasing Southerly winds that start clocking as the front approaches. The wave heights quickly become large not far offshore. Just at the peak of the southerly pattern, the winds take an abrupt North, NW turn and blow hard for days sending big swells to Puerto Rico and Northern Caribbean. Northerly gales blowing against the Gulf Stream current make for extremely hazardous sea states. Sustained winds from 30 to 70 knots are not uncommon on a regular basis.

This unnerves less experienced skippers, instinct kicks in, and the common tactical error is made when boats head inshore to find refuge in the Sound. Unfortunately,  the Oregon, Hatteras, and Ocracoke Inlets are not friendly under the best of conditions and are difficult to the most experienced local mariners. The inlet waters are shallow and the charts cannot keep up with shifting sand bars and transient channels. Each of these inlets have regular dredging year round just to keep them navigable for ferry service and local fishermen.

Crew Experience

Experienced mariners know not to attempt rounding the Capes in Winter.  This particular crew underestimated the conditions significantly. Worse yet, the reported float plan was to motor around the Capes heading Southbound. They did not intend to use the sails, and confirmed they were motoring with sails down when the problems began. A sloop without a sail up in rough seas is not a pleasant experience and the pounding is hard on the equipment. In even the smallest swell, a keelboat rides much better with side pressure in the sails to to decrease rolling. In nearly critical gulfstream conditions, a sloop without the sails up will be rocking and rolling, pitching drastically. The unstable pitching has a trickle down effect on the systems aboard the vessel – stirring up sediment in the diesel tanks, clogging fuel filters, tossing gear around the cabin – eventually the crew become disenchanted and fatigued which compounds all the problems aboard. A skipper must be able to sail a sailboat when cruising offshore. The engine is an auxiliary system designed as a backup or an augmentation.  The decision to motor with sails down was the first of several tactically bad decisions, the worst of which was to head inshore near the capes and attempt the inlet at night.

Maybe in some locations it makes sense to get closer to land when the going gets rough, but that strategy is not good near the 3 North Carolina Capes. Storms passing make breaking wave conditions in the inlets, and the Capes are riddled with shoals and sandbars near shore and farther from shore. Most of these shoals and sandbars are shifting and not charted well. In this case, the crew lost the chartplotter after losing the power supply at night in challenging conditions. It was a critical failure. Without solid experience and quick reflexes in wise courses of action, it can be just a matter of minutes before a vessel finds itself aground. In storm conditions with waves over 6 – 10 feet the shallow spots will have large breaking waves. Boats sometimes can opt to put out very long anchor tackle, but it can fail too under such strong forces. With the right anchor line and ground tackle, this strategy can work but you have to prepare in advance and still need local knowledge of the shoals off the beach. We often see shrimp boats spending the night on anchor just off the beach, but these commercial watermen know where to position themselves safely, and they are equipped to stay on anchor in rough conditions. In this case, the crew were underway approaching the inlet at night with power failures on board and no sails set.

Salvage Efforts

The vessel grounded near the beach at the South tip of Ocracoke between midnight and 2am on November 2 and the Sheriff’s Office assisted the crew safely off the boat. It landed close enough to shore that the crew was able to walk ashore albeit through strong current and wave action. Word of the wreck was spread to various marine professionals in the area to help with the salvage, including my company Phillips Boatworks. 

Insurance and Red Tape

Immediate recovery is best if possible, but hardly ever happens. There are many moving parts that have to be managed and need to all fall into place. The goal in this case was to find a way to save the vessel from breaking up in the surf, but the longer the boat sits the worse the situation becomes. Work cannot begin without money, permits, men, and equipment. Scarcity is an issue on the Outer Banks and even more so in Ocracoke. The island communities are small. Manpower and heavy equipment do not sit idle, particularly in winter when the vacationers have gone home and repairs and infrastructure projects are underway. The boat owner needs to elect a primary salvage manager quickly. Nothing can begin till that decision is made because money must be transferred.  Men and resources have to be shifted. There are limited salvage resources locally, but other resources have to be brought in from hours away. In this case, because the boat was grounded near Ocracoke, everything needed to come over by ferry or by boat. The ferry ride is more than one hour and this time of year the schedule of ferries is reduced and subject to weather delay.

Time Is The Enemy Of Recovery

On Thursday morning November 2nd, I was the first salvage contractor on the scene.  At that time, the weather models indicated calm conditions for the next several days and that stirred hope that the vessel could be rescued and towed away for repairs. On this, the owner contracted my company, Phillips Boatworks, to begin salvage efforts hoping that we could handle the sailboat and rigging with the least damage possible.  Tragically, there were problems with the insurance policy and the claim was immediately denied leaving the cost of recovery to be financed entirely by the owner. When this happens,  my company and most salvage contractors can only engage when funds are paid in advance with more held in escrow. This meant further delays before the work could begin. The owner wired a deposit mid-afternoon on Nov-2, but it was already too late in the day to gather resources onto the ferry to board the boat before sunset so that critical first day was lost. 

Sadly, the weather and ocean keep churning. A safe and effective salvage requires a weather window. In this case, the vessel landed in a very bad spot in the inlet.  Because of high current and seaside wave action every delay was a serious problem.  When my team arrived on the scene Friday morning with the first tranche of equipment, the wind was blowing upwards of 20 knots and the current was ripping through over the boat at about 5 knots. It was high tide. Sand had already filled most of the interior of the boat, and we estimated that not even a large 4” trash pump could keep up with how fast the water and sand were coming in. We set up transfer lines and prepared to try again to seal the boat, evaluate the damage, and set pumps at low tide that afternoon. Tragically, by low tide the boat was totally under the sand and fully underwater.  I was  able to go on board into the cockpit, and stick just my head into the cabin at low tide. In the process, I was fighting 3-5 knots of current sweeping over the deck under breaking waves. We determined with the financial, weather, and time constraints, that constructive recovery efforts were no longer possible.

It is amazing how fast the sea can take a large vessel. Any beach goer who has stepped into the ocean with the current ripping sideways has noticed what happens to the sand in the current around your feet. A hole is dredged around the upcurrent side quickly and then the pedestal of sand your weight was holding down quickly collapses. The same thing happens with a heavy boat sitting in the strong current and shallow water. This process repeats itself until the seabed gets back to its equilibrium, which means the heavy object is now under the sand. This happened very fast in this case which was amplified by higher than expected sideshore winds. Less than 24 hours had passed since the boat ran aground.

From Salvage to Clearing

Strategies for saving the vessel now seemed unlikely, even the local Crane service would have issues getting its 95,000 lb crane 2 miles across the beach. At this point, the boat could possibly be broken apart and the debris removed, but given the depth of the wreck, distance from shore, depth of the water approach, the strength of the current, and the serious wave action at this particular location even breaking up the wreck has significant challenges.

The Blessing of a Safe and Uninjured Crew

No one was injured or killed during the loss of the vessel or salvage attempts. The owner is hopeful that he can resurrect his dream of sailing Cuba and the Caribbean with his wife and kids, and he is realistic about the lessons learned. Mariners must give the North Carolina Capes their due respect. The Capes have claimed many ships and many more lives rightfully earning the moniker “Graveyard of the Atlantic”. 

Constructive suggestions for mariners….

• When possible, take the Intercoastal especially in the Fall, Winter, and Early Spring
• Do not go short handed or with inexperienced crew. Each member needs to be competent to stand watch
• Make sure your vessel and equipment are up to the challenge of the potential sea state.
• Getting past the 3 impassable inlets takes a while, and the weather changes quickly
•  It is about 300 miles from the Chesapeake to Beaufort NC and 400 miles to Southport.  A typical sailing yacht averages 100-150 miles per day on a good day.  Against the wind and waves sometimes 0 – 50 miles forward (VMG) per day.
• Cold Fronts and Gale conditions can pass as frequently as 2 times per week in the winter which makes it almost a sure bet that gale conditions will be encountered in a 2 – 5 day rounding.
• Beaufort is a much better inlet but still challenging at night or in bad weather and Cape Fear is still to be rounded.
• From November to April, going outside around the Capes is treacherous at best

Nevertheless, sailing is a wonderful adventure. It can be dangerous, but just like flying an airplane, proper training and well maintained equipment can mitigate the dangers and allow for good times and lifelong adventures on the seas. Safe seamanship requires good teachers, ongoing practice, and experience building. Start with small challenges and work your way into harder challenges gradually, not all at once. Time your passages in the right season. Err on the side of caution. Expect equipment failures. Plan contingencies. Stay calm and sail your sailboat.

The Author, Jay Phillips

Sailing professionally since 1991, Phillips has roughly 100,000 or more blue water miles in sailing and motor vessels and has been teaching basic keelboat, racing and offshore passagemaking for 32 years. His company Phillips Boatworks offers charters, salvage services, sails and rigging, and boatbuilding out of the Hatteras Sailing Center in Buxton. Phillips was the developer of the Stiletto X Series Catamarans and now the Designer and Builder of the new pH-10 and pH-850 performance catamarans. If you are interested in learning safe passage making habits and skills, Jay and his wife Meg founded Hatteras Community Sailing (HCS) to further maritime education on Hatteras Island.  Their passion is in training the next generation of sailors. HCS is a US SAILING recognized learning facility for all ages, and teaches all levels of racing and cruising education from Opti Kids and dinghy sailing to basic keelboat upwards through offshore passagemaking. For more information please visit phillipsboatworks.com and hatterassailing.org

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What Was the Largest Wave Ever Recorded?

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Scientists have long been fascinated by the ocean's dynamic nature, where the force of the water collides with atmospheric phenomena to create waves of monumental size.

The largest wave ever recorded was documented by researchers who analyze and predict marine and weather patterns. These measurements help not only in understanding the ocean's capabilities but also in preparing for natural disasters.

So, what is the tallest wave ever recorded? Let's find out!

The Lituya Bay Tsunami and the Biggest Wave Ever Recorded

What are rogue waves, what is the highest rogue wave ever recorded, 10 other places with record-breaking waves, the biggest wave ever surfed.

In the serene landscape of Lituya Bay, Alaska, the evening of July 9, 1958, marked a monumental event. Seismic activity along the Fairweather Fault, which runs west of Juneau along the Alaska Panhandle, triggered a massive earthquake and dislodged an enormous amount of earth.

This landslide, involving approximately 90 million tons of rock, plunged into the narrow Gilbert Inlet at tremendous speed. The displacement caused by the glacier that dropped into the inlet was so immense that it created a tsunami unlike any recorded before or since.

As this wave hit the opposite shoreline, it generated a staggering force, causing the wave crest to break with such power that it scoured trees and soil from slopes, reshaping the terrain.

The entire length of the inlet felt the impact as the wave crest broke, reaching a height of 1,720 feet (524 meters) above sea level. To put this in perspective, the Empire State Building is 1,250 feet ( 380 meters ) tall, making the wave 470 feet (143 meters) taller than the skyscraper.

A fishing boat anchored at the mouth of the bay witnessed the massive tsunami's might as it reshaped Lituya Bay in mere moments. The boat managed to ride the wave , a testament to both the mariners' luck and the unique conditions of the bay.

The Lituya Bay tsunami not only became a crucial study point for research but also solidified its status as the largest recorded wave.

A rogue wave is an unusually large and unexpected wave that can appear suddenly in the open ocean , posing significant dangers to ships. Also referred to as walls of water, they're disproportionately tall and steep, compared to the surrounding sea conditions.

Historically, rogue waves were considered mythical by sailors and largely unrecognized by scientists until they were conclusively detected by modern instruments. They're are often characterized as being more than twice the height of surrounding waves, making them some of the tallest waves observed at sea.

Unlike tsunamis, which are generated by underwater disturbances like earthquakes, rogue waves seem to arise due to the merging of several smaller waves, which, due to various oceanic conditions, combine their energies into a single, exceptionally powerful wave.

This process results in towering walls of water that rise abruptly and without warning, capable of causing catastrophic damage and even capsizing vessels.

The study of rogue waves has been pivotal in understanding the dynamics of the open ocean, as these outliers challenge traditional wave models that once predicted their near impossibility. Modern marine research continues to explore how wind conditions, ocean currents and other factors contribute to the formation of these ocean phenomena.

The highest rogue wave ever recorded measured 84 feet (25.6 meters) in height and was detected by a Norwegian oil platform in the North Sea in 1995, making it the most extreme rogue wave observed in modern maritime history.

Researchers studying this wave noted that it occurred in a relatively harsh sea state, characterized by strong winds and significant wave heights, which likely contributed to its extreme formation.

As the quest for bigger and more thrilling waves continues, certain destinations around the world have become known for record-breaking swells. Each location has its unique geological and oceanographic conditions that produce some of the most extreme waves known to humankind.

From the legendary barrels of Tahiti to the ominous swells of Ireland's West Coast, these destinations challenge the limits of big wave surfing. Here are some of the most renowned spots where the giants of the ocean come to life.

1. Nazaré, Portugal

Nazaré , Portugal, is renowned for its monstrous waves, attracting big wave surfers from around the globe. The underwater Nazaré Canyon funnels swell energy directly to Praia do Norte, producing some of the most extreme waves ever surfed.

2. Pe'ahi /Jaws, Maui

Jaws, also known as Pe'ahi, is a mecca off the shores of Maui for surfers seeking the challenge of mammoth waves. Known for its powerful winter swells, Jaws generates towering walls of water that offer a thrilling ride for those skilled enough to navigate its massive breaks.

This destination is a cornerstone in the history of big wave surfing, regularly drawing a crowd to witness its spectacular swells.

3. Cortes Bank, California

Located off the coast of Southern California, Cortes Bank is an underwater seamount that produces some of the biggest waves on the planet.

This spot is unique due to its remote location and the fact that its waves break miles from shore over a submerged island, making it a dangerous yet irresistible challenge for surfers.

4. Mavericks, California

Mavericks in Northern California is infamous for its cold, shark-infested waters and massive waves that crash onto a shallow reef. This spot has become a storied venue in big wave surfing lore, hosting prestigious competitions that test the limits of even the most seasoned surfers.

5. Puerto Escondido, Mexico

Known as the "Mexican Pipeline," Puerto Escondido offers some of the most powerful and dangerous waves in the world. The beach break here is famed for its consistency and ferocity , attracting surfers eager to tackle its fast-moving tubes and thick, heavy barrels.

6. Waimea, Hawaii

Waimea Bay on Hawaii's North Shore is a historic site in the world of big wave surfing. It was one of the first spots where surfers began to challenge the big waves, and it continues to be a proving ground for those looking to make their mark in the sport. The iconic waves draw spectators and surfers alike each winter.

7. Teahupo'o, Tahiti

Teahupo'o in Tahiti is perhaps best known for its visually stunning yet dangerously shallow reef break. The waves here break so close to the surface that they form a thick, hollow tube, providing one of the most challenging rides available to big wave surfers — a true test of skill and nerve.

8. Cloudbreak, Fiji

Cloudbreak off the coast of Fiji is a world-class surf spot famous for its long, winding waves and pristine beauty. This reef break can hold swells that produce significant wave heights, offering a paradise for those looking to experience big wave surfing amidst the isolated splendor of the South Pacific.

9. Mullaghmore Head, Ireland

Mullaghmore Head along Ireland's West Coast is renowned for its monstrous winter swells that attract surfers from across the globe. The cold Atlantic waters here give rise to some of the most intimidating waves in Europe, driven by deep ocean swells that crash into its rugged coastline.

10. Belharra, France

Belharra, off the coast of France, is another European hotspot for giant waves. This deep water reef comes alive during the winter when conditions align to produce massive swells that can be seen and heard from miles away.

It’s a favorite challenge for big wave surfers in the region, adding to the allure of Europe's unlikely big wave surfing scene.

In the realm of big wave surfing, one question often echoes through the community: "Has anyone surfed a 100-foot wave?" While that exact milestone remains officially unconfirmed, a record was broken in the legendary swells at Nazaré, Portugal.

In 2020, German surfer Sebastian Steudtner rode a 86 foot wave at Nazaré. Although precise measurements can vary, this ride entered the record books and captured the world's attention, symbolizing the pinnacle of what is humanly possible in big wave surfing.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.

Please copy/paste the following text to properly cite this HowStuffWorks.com article:

Ecuadorians head to polls to toughen fight against gangs behind wave of violence

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Ecuadorians headed to the polls Sunday in a referendum touted by the country’s fledgling leader as a way to crack down on criminal gangs behind a spiraling wave of violence.

The majority of 11 questions posed to voters focus on tightening security measures. Proposals include deploying the army in the fight against the gangs, loosening obstacles to extradition of accused criminals and lengthening prison sentences for convicted drug traffickers.

Ecuador, traditionally one of South America’s most peaceful countries, has been rocked in recent year by a wave of violence, much of it spilling over from neighboring Colombia, the world’s largest producer of cocaine. Last year, the country’s homicide rate shot up to 40 deaths per 100,000, one of the highest in the region.

President Daniel Noboa has rallied popular support by confronting the gangs head on. That task became more urgent in January when masked gunmen, some on orders from imprisoned drug traffickers, terrorized residents and took control of a television station while it was live on the air in an unprecedented show of force.

Following the rampage, the 36-year-old leader decreed an “internal armed conflict,” enabling him to use emergency powers to deploy the army in pursuit of about 20 gangs now classified as “terrorists.”

The referendum seeks to extend those powers and put them on firmer legal ground.

“We can’t live in fear of leaving our homes,” said Leonor Sandoval, a 39-year-old homemaker, after voting for all 11 of the proposals. Results were expected Sunday evening.

But in recalling the law-and-order policies of El Salvador’s wildly popular president, Nayib Bukele, a fellow millennial, they could also boost Noboa politically as he prepares to run for reelection next year.

Noboa, the scion of a wealthy banana exporting family , is serving the final 18 months of a presidential term left vacant when fellow conservative Guillermo Lasso resigned amid an investigation into alleged corruption by congress. He was elected following a shortened but bloody campaign that saw one of his top rivals brazenly assassinated while campaigning .

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Middle East latest: Netanyahu vows to 'increase pressure' on Hamas; Iran 'displayed power' in attack on Israel, Supreme Leader claims

Iran's Supreme Leader Ayatollah Ali Khamenei has spoken for the first time since his country attacked Israel. It follows news of Palestinians being killed in Rafah and the West Bank, and the IDF launching strikes in Lebanon.

Sunday 21 April 2024 17:50, UK

• Israel-Hamas war

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• Iran 'displayed power' in attack on Israel, Supreme Leader insists - despite failure
• Sean Bell: New details hint at impact of Israeli strike on Iran
• 13 children from same family killed in strike on Rafah, hospital says
• IDF sanctions a 'dangerous precedent', senior Israeli politician warns
• At least 14 Palestinians killed in West Bank raid, authorities say
• Israel says it has attacked 'terrorist targets' in Lebanon
• US Congress approves aid package for Israel 
• Analysis: Iran isn't biggest threat to the coalition right now
• Live reporting by Bhvishya Patel and (earlier)  Narbeh Minassian

Israel war cabinet member Benny Gantz has spoken with US Secretary of State Antony Blinken and asked him to reconsider the decision to sanction the IDF's Netzah Yehuda battalion, the American news website Axios reports, citing Mr Gantz's office.

For context : This weekend a report from Axios claimed the US was expected to announce sanctions within days on the IDF battalion for human rights violations in the occupied West Bank.  

Prime Minster Benjamin Netanyahu has already responded, warning it is "forbidden" to sanction the IDF.

The Axios report adds it would be the first time the US has imposed sanctions on an Israeli military unit.

Israel and Iran have been at war for decades but they have been fighting in the shadows.

Analysts believe both countries are now trying to ease tensions following a series of escalatory attacks between them.

Here, our international affairs editor Dominic Waghorn   explains how we got here and what could be next.

We have been reporting today on Israeli strikes on the southern Gaza city of Rafah overnight which killed 22 people, including 18 children, according to health officials.

Now, the IDF has responded to the overnight strikes.

"At the given times, the IDF struck several military targets of the terrorist organisations in Gaza including military compounds, launch posts and armed terrorists," it said in a statement.

For context : Israel has carried out near-daily air raids on Rafah, where more than half of Gaza's population of 2.3 million have sought refuge from fighting elsewhere.

It has also vowed to expand its ground offensive to the city on the border with Egypt despite international calls for restraint, including from the US.

Israel will "increase the political and military pressure on Hamas in the coming days", Benjamin Netanyahu has said.

Speaking before the Jewish holiday of Passover that starts tomorrow, the Israeli leader said all proposals for the release of hostages had been "outright rejected by Hamas".

"In the coming days we will increase the military and political pressure on Hamas because this is the only way to free our hostages and achieve our victory," he said.

He also responded to reports of imminent US sanctions on the IDF religious battalion Netzah Yehuda saying: "If anyone thinks they can impose sanctions on a unit in the IDF I will fight it with all my might."

The balance between the right to protest and the rights of everyone else had been completely lost, a charity that protects British Jews from antisemitism has said. 

We have been reporting this weekend on a Met Police officer who was recorded preventing a Jewish man from crossing a road by a pro-Palestinian march because he is "openly Jewish".

The force has since apologised.

Responding to the incident in a statement on X, the Community Security Trust (CST) noted that since 7 October it had seen a "record increase in anti-Jewish hate crime against a backdrop of constant anti-Israel hate demonstrations".

It said CST was working with the police to protect the Jewish community but despite "all the good work" there had been "mistakes".

"This latest case fits that profile, with the context and detail lost in the heat of controversy. An individual officer tried to do the right thing but ended up making things worse in a very difficult moment," the charity said.

The broader question, the CST said, was "how much longer these costly and disruptive protests will be allowed to continue".

"It feels like any balance between the right to protest and the rights of everyone else had been completely lost, with extremists the only ones to benefit, Jews the first to suffer and the police often caught in the middle," it added.

The Israeli military says its soldiers shot two Palestinians who tried to attack them in the West Bank this morning. 

We reported earlier today the IDF claimed two Palestinians tried to stab and shoot its soldiers near the city of Hebron (see our 9.13am post). 

One was reported dead, but now the Palestinian health ministry says both have been killed.

The Israeli military said: "One of the terrorists attempted to stab IDF soldiers that were in the area, who responded with live fire and neutralised him." 

The force added: "At the same time, the other terrorist opened fire at the soldiers, who responded with live fire and neutralised him too."

The official Palestinian news agency WAFA, quoting local sources, said ambulance crews were prevented from reaching the two men.

Palestinian security sources told WAFA the two men, aged 18 and 19, died and that they were still unable to collect their bodies.

A Tory peer has called for the Gaza conflict to end "immediately" as he criticised Israel for an alleged attack on Rafah that killed at least 22 people.

Israel has been carrying out air raids on the southern Gazan city almost daily, with the latest round reportedly killing 17 children of the same extended family overnight (see our 1.46pm post).

Lord Ahmad, a minister at the foreign office, said on X: "Appalled by the Israeli strike on a residential apartment in the densely populated Rafah in Gaza, which resulted in more children being killed.  

"We must stop this fighting immediately and bring an end to this conflict."

It comes just one day after nine people were reportedly killed in another airstrike on the city, including six children, according to Palestinian authorities.

Hundreds of thousands of Palestinians are seeking safety in Rafah, having fled attacks elsewhere in the Gaza Strip.

The IDF says it is unaware of any US sanctions against one of its battalions, after a report claimed Washington is planning such a step against a unit for alleged human rights violations in the West Bank (see our 8.14am post).

The military said that its Netzah Yehuda battalion - which is reportedly the target of potential sanctions - is an active combat unit that operates according to the "principles of international law".

"Following publications about sanctions against the battalion, the IDF is not aware of the issue," military spokesperson Daniel Hagari said. 

"If a decision is made on the matter it will be reviewed. 

"The IDF works and will continue to work to investigate any unusual event in a practical manner and according to law."

We reported this morning the Board of Deputies of British Jews has called for an urgent meeting with Met Police chief Sir Mark Rowley, following an officer's handling of an antisemitism campaigner near a pro-Palestinian march (see our 10.14am post).

The group has now said it will meet with Sir Mark later this week, along with the Jewish Leadership Council and antisemitism charity CST.

The Campaign Against Antisemitism, whose chief executive Gideon Falter was the campaigner called "openly Jewish" by a police officer last weekend, has told Sky News it has not been invited to the meeting.

Mr Falter had earlier called for Sir Mark to resign, as did former home secretary Suella Braverman.

In a video of the incident, an officer appears to prevent Mr Falter from crossing the road and tells him: "You are quite openly Jewish. 

"This is a pro-Palestinian march. I am not accusing you of anything, but I am worried about the reaction to your presence."

A government source said Prime Minister Rishi Sunak is "appalled" at what happened.

The Met Police has apologised.

The number of people killed in Israeli strikes on the southern Gaza city of Rafah overnight has risen to 22, Palestinian health officials say.

One of the strikes killed 17 children and two women of the same extended family, according to hospital records. Earlier, these records showed 13 children of the same family had died (see our 10.38am post).

First responders are still searching the rubble, The Associated Press reports.

Another strike killed a married couple and their three-year-old child, according to the nearby Kuwaiti Hospital, which says the woman was pregnant and doctors managed to save the baby.

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