A sneaker wave, also known as a sleeper wave, or in

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as a king wave, is a disproportionately large coastal wave that can sometimes appear in a wave train without warning.

Terminology

The term "sneaker wave" is popular rather than scientific, derived from the observation that such a wave can "sneak up" on an unwary beachgoer. There is no scientific coverage of the phenomenon as a distinct sort of wave with respect to height or predictability as there is on other extreme wave events such as

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...

s or

rogue wave Rogue waves (also known as freak waves, monster waves, episodic waves, killer waves, extreme waves, and abnormal waves) are unusually large, unpredictable, and suddenly appearing surface waves that can be extremely dangerous to ships, even to lar ...

s, and little or no scientific evidence has been gathered to identify, describe, or define sneaker waves. Although the term "rogue wave" — meaning an unusually tall or steep wave in mid-ocean — is sometimes used as a synonym for "sneaker wave," one American oceanographer distinguishes "rogue waves" as occurring on the ocean and "sneaker waves" as occurring at the shore, while the

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loosely defines rogue waves as offshore waves that are at least twice the height of surrounding waves and sneaker waves as waves near shore that are unexpectedly and significantly larger than other waves reaching shore at the time.Johnson, Craig, and Jason Hanna, "Waves that injured surf audience were sneaky, but not 'rogue'," CNN, February 15, 2010 Accessed 4 December 2021
/ref> Scientists do not yet understand what causes sneaker waves,Tomlinson, Jessica, "What You Don’t Know About Oregon Coast Sneaker Waves Could Kill You," That Oregon Life, April 1, 2021 Accessed 4 December 2021
/ref> and their relationship to rogue waves, if any, has not been established. In a 2018 paper,

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researchers wrote that sneaker waves form in offshore storms that transfer wind energy to the ocean surface. The resulting waves then arrive along a coastline during periods of calm weather, and the greater amount of energy they contain compared to the regular waves that preceded them causes them to travel far higher up the shore than the other waves. As of 2021, the

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in the

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viewed ocean conditions along the

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as favorable for sneaker waves when an offshore storm generates waves with a particularly long period — perhaps longer than 15 seconds — between swells, allowing the swells to build considerable force before reaching shore, where they might appear either as conventional large waves or as sneaker waves.

Characteristics

Sneaker waves appear suddenly on a coastline and without warning;"Sneaker/High Waves and Log Rolls Can Be Deadly," National Weather Service Accessed 4 December 2021
/ref> generally, it is not obvious that they are larger than other waves until they break and suddenly surge up a beach. A sneaker wave can occur following a period of 10 to 20 minutes of gentle, lapping waves. Upon arriving, a sneaker wave can surge more than beyond the foam line, rushing up a beach with great force. In addition to containing a large volume of rapidly surging water, a sneaker wave also tends to carry a large amount of sand and gravel with it. It can be strong enough to break over rocks and float or roll large, waterlogged logs lying on the beach weighing several hundred pounds, moving them up the beach during the landward surge and then back down toward the ocean as the wave retreats. Sneaker waves appear to be more common along steep coastlines than in areas with broader, more gently sloped beaches.

Hazards

The unpredictability of sneaker waves and their tendency to arrive suddenly after lengthy periods of gentle, lapping waves makes it easy for them to surprise unwary or inexperienced beachgoers; because they are much larger than preceding waves, sneaker waves can catch inattentive

swimmers Swimming is the self-propulsion of a person through water, or other liquid, usually for recreation, sport, exercise, or survival. Locomotion is achieved through coordinated movement of the limbs and the body to achieve hydrodynamic thrust that r ...

, waders, and other people on beaches and ocean

jetties A jetty is a structure that projects from land out into water. A jetty may serve as a breakwater, as a walkway, or both; or, in pairs, as a means of constricting a channel. The term derives from the French word ', "thrown", signifying somet ...

and wash them into the sea. The force of a sneaker wave's surge and the large volume of water rushing far up a beach is enough to suddenly submerge people thigh- or waist-deep, knock them off their feet, and drag them into the ocean or trap them against rocks. Many coastlines more prone to sneaker waves lie in colder parts of the world where beachgoers tend to wear heavier clothing, and the amount of sand and gravel in a sneaker wave can quickly fill clothing and footwear such as boots with sediment that weighs a person down as he or she is swept up a beach and then back into the sea, increasing the chances of drowning. Floating and rolling logs in a sneaker wave also pose a danger, as they can badly injure people as well as pin people down when they come to rest, and it can be difficult or impossible to move such a log before a person pinned by it drowns as later waves arrive and fill the person's lungs with water and sediment.

Geographic distribution

Sneaker waves are mainly referred to in warnings and reports of incidents for the coasts of

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and

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(including the

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's beaches, especially Ocean Beach, Baker Beach, and those that face the

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) (e.g. from

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to the California–

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border), Oregon, and

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in the

Western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that id ...

. Sneaker waves also occur on the coast of

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, especially the province's southern coast, because they commonly occur on the west coast of

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian Provinces and territories of Canada, province of British Columbia. The island is in length, in width at its widest point, and in total area, while are o ...

(including

Tofino Tofino ( ) is a town of approximately 2,516 residents on the west coast of Vancouver Island in the Canadian province of British Columbia. The District of Tofino is located at the western terminus of Highway 4 on the tip of the Esowista Penins ...

Ucluelet Ucluelet (, also Ukee) is a district municipality (population 1,717) on the Ucluelet Peninsula on the west coast of Vancouver Island in British Columbia, Canada. Ucluelet means "people of the safe harbour" in the indigenous Nuu-chah-nulth (No ...

, and

Cape Scott Provincial Park Cape Scott Provincial Park extends from Shushartie in the east, then westward around Cape Scott and south to San Josef Bay. This coastline comprises the northern tip of Vancouver Island, British Columbia. The provincial park is about northwest ...

). Sneaker waves are common on the southern coast of

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, and warning signs were erected at Reynisfjara and Kirkjufjara beaches, following three unrelated tourist deaths at those beaches over several years, the third of them in January 2017. In

, where they are known as "king waves," sneaker waves occur especially in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

and

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

, where they can be a hazard for rock fishermen. Along much of the

, sneaker waves kill more people than all other weather hazards combined. In Oregon, 21 deaths were attributed to sneaker waves from 1990 through March 2021, most of the deaths occurring between October and April, although sneaker waves also occurred at other times of year. A sneaker wave incident gained worldwide media attention when two large waves suddenly and unexpectedly struck a crowd watching the Mavericks surfing competition at

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in Princeton-by-the-Sea, California, on February 13, 2010, breaking over a seawall onto a narrow beach and injuring at least 13 people. The incident was caught on film.

Seventh wave

In many parts of the world, local

folklore Folklore is shared by a particular group of people; it encompasses the traditions common to that culture, subculture or group. This includes oral traditions such as tales, legends, proverbs and jokes. They include material culture, ranging ...

predicts that out of a certain number of waves, one will be much larger than the rest. "Every seventh wave" or "every ninth wave" are examples of such common beliefs that have wide circulation and have entered popular culture through music, literature, and art. These ideas have some scientific merit, due to the occurrence of wave groups at sea, but there is no explicit evidence for this specific phenomenon, or that these wave groups are related to sneaker waves. The saying is likely derived more from a cultural fascination with certain numbers, and it may also be designed to educate shore-dwellers about the necessity of remaining vigilant when near the ocean.

Terminology

Characteristics

Hazards

Geographic distribution

Seventh wave

See also