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Sneaker wave

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Sneaker wave at Bolinas, California

A sneaker wave, also known as a sleeper wave, or in Australia as a king wave, is a disproportionately large coastal wave that can sometimes appear in a wave train without warning.


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 tsunamis or rogue waves, 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,[1] while the National Oceanic and Atmospheric Administration 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.[2] Scientists do not yet understand what causes sneaker waves,[3] and their relationship to rogue waves, if any, has not been established.

In a 2018 paper, Oregon State University 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.[4] As of 2021, the National Weather Service in the United States viewed ocean conditions along the United States West Coast 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.[5]


Sneaker waves appear suddenly on a coastline and without warning;[6] 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.[6] Upon arriving, a sneaker wave can surge more than 150 feet (50 m) beyond the foam line, rushing up a beach with great force.[6] 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.[6] Sneaker waves appear to be more common along steep coastlines than in areas with broader, more gently sloped beaches.[6]


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;[6] because they are much larger than preceding waves, sneaker waves can catch inattentive swimmers, waders, and other people on beaches and ocean jetties 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.[6] Many coastlines more prone to sneaker waves lie in colder parts of the world where beachgoers tend to wear heavier clothing; the amount of sand and gravel in a sneaker wave can quickly fill such 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.[6] 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.[6]

Geographic distribution[edit]

Sneaker waves are mainly referred to in warnings and reports of incidents for the coasts of Central and Northern California (including the San Francisco Bay Area's beaches, especially Ocean Beach,[7] Baker Beach,[8] and those that face the Pacific Ocean,[9] e.g. from Big Sur to the California–Oregon border), Oregon, and Washington in the Western United States.[10][11][12][13][14][15] Sneaker waves also occur on the coast of British Columbia in Western Canada, especially the province's southern coast, because they commonly occur on the west coast of Vancouver Island (including Tofino, Ucluelet, and Cape Scott Provincial Park).[16][17][18][19] Sneaker waves are common on the southern coast of Iceland, 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.[20] In Australia, where they are known as "king waves," sneaker waves occur especially in Western Australia and Tasmania, where they can be a hazard for rock fishermen.[21]

Along much of the United States West Coast, sneaker waves kill more people than all other weather hazards combined.[6] In Oregon, 21 deaths were attributed to sneaker waves from 1990 through March 2021,[3] most of the deaths occurring between October and April, although sneaker waves also occurred at other times of year.[3]

A sneaker wave incident gained worldwide media attention when two large waves suddenly and unexpectedly struck a crowd watching the Mavericks surfing competition at Mavericks in Princeton-by-the-Sea, California, on February 13, 2010, breaking over a seawall onto a narrow beach and injuring at least 13 people.[2][22] The incident was caught on film.[2][23]

In March 2014, a massive wave struck Roi-Namur in Kwajalein Atoll in the Marshall Islands on an otherwise calm, sunny day, penetrating well inland, flooding parts of the island and swamping coastal roads.[24]

On September 18, 2023, a sneaker wave smashed into a beachside restaurant at Marina Beach near Southbroom, South Africa, injuring seven people. One restaurant patron was swept out to sea but rescued by lifeguards. The wave was filmed.[25]

Rio de Janeiro's Barra de Tijuca beach in Brazil experiences sneaker waves, known locally as ressaca waves. It also is a steep beach and a December 2023 news film shows the whole beach being cleared by a sneaker wave.[citation needed]

On 20 January 2024, one or more sneaker or rogue waves struck the United States Army′s Ronald Reagan Ballistic Missile Defense Test Site on Roi-Namur in Kwajalein Atoll in the Marshall Islands, breaking down the doors of a dining hall, knocking several people off their feet, moderately to severely damaging the dining hall, the Outrigger Bar and Grill, the chapel, and the Tradewinds Theater, and leaving parts of the island, including the automotive complex, underwater. The flooding of the dining hall was filmed. The wave or waves penetrated 300 feet (100 m) inland and probably were between 29 and 40 feet (8.8 and 12.2 m) tall amid a significant wave height of 10 feet (3 m) to 15 feet (5 m).[26]

Seventh wave[edit]

In many parts of the world, local folklore 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.[27][28] These ideas have some scientific merit, due to the occurrence of wave groups at sea,[29] 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,[citation needed] and it may also be designed to educate shore-dwellers about the necessity of remaining vigilant when near the ocean.

See also[edit]


  1. ^ Miller, Craig (22 October 2013). "What Makes 'Sneaker Waves' so Sneaky -- and Dangerous". KQED. Retrieved 13 July 2020.
  2. ^ a b c Johnson, Craig, and Jason Hanna, "Waves that injured surf audience were sneaky, but not 'rogue'," CNN, February 15, 2010 Accessed 4 December 2021
  3. ^ a b c 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
  4. ^ Anonymous, "Parents of boy swept to sea didn’t know about the hidden dangers of California’s sneaker waves," Nexstar Media Inc. via the Associated Press, May 4, 2021 Accessed 4 December 2021
  5. ^ "Caution Urged on Oregon Coast: Sneaker Wave Dangers This Weekend," Oregon Coast Beach Connection, October 1, 2021 Accessed 4 December 2021
  6. ^ a b c d e f g h i j "Sneaker/High Waves and Log Rolls Can Be Deadly," National Weather Service Accessed 4 December 2021
  7. ^ Ted Andersen (28 September 2018). "California's deadliest beach is in the Bay Area". San Francisco Chronicle. Retrieved 10 August 2020.
  8. ^ Malcolm Glover and Dan Levy (23 December 2000). "Teen Swept Away by 'Rogue' Wave / Boy was at Baker Beach posing for a picture". San Francisco Chronicle. Retrieved 10 August 2020.
  9. ^ Amy Graff (21 January 2020). "Sneaker wave danger at Bay Area beaches: 'Never turn your back to the ocean'". San Francisco Chronicle. Retrieved 10 August 2020.
  10. ^ "Sleeper waves have led to other drownings in Humboldt County beaches". San Francisco Chronicle. 24 October 2006. Retrieved 1 August 2020.
  11. ^ "Rogue or Sneaker Waves". Mary Donahue. Retrieved 1 August 2020.
  12. ^ "Dangerous Sneaker waves possible on Central Coast". KION5/46. 26 December 2019. Retrieved 1 August 2020.
  13. ^ "Sneaker/High Waves and Log Rolls Can Be Deadly". National Weather Service. Retrieved 13 July 2020.
  14. ^ "Safety Issues Associated with Beaches". National Park Service.
  15. ^ "New Residents: Welcome to Newport" (PDF). Newport, Oregon Police Department. 17 April 2018. Retrieved 13 July 2020.
  16. ^ "Cape Scott Provincial Park: Hiking". Retrieved 28 July 2020.
  17. ^ "Hiking and Outdoor Safety". Retrieved 16 July 2020.
  18. ^ "Dangerous Sneaker Waves". 18 April 2016. Retrieved 20 July 2020.
  19. ^ "Giant wave crashes into Tofino resort's oceanfront" (video). 18 January 2018. Retrieved 13 July 2020.
  20. ^ ""Terrible situation" at Iceland's Reynisfjara beach - security to be improved". Iceland Monitor. 12 January 2017. Retrieved 13 July 2020.
  21. ^ "King wave almost claims more at Salmon Holes". ABC News (Australia). 12 May 2011. Retrieved 13 July 2020.
  22. ^ Blackstone, John, "Surfing Spectators Struck by 50-Foot Wave," CBS News, February 14, 2021 Accessed 4 December 2021
  23. ^ ketchdust, "Mavericks February 13 2010 Rogue Wave," Youtube, Accessed 31 December 2023
  24. ^ Greshko, Michael (25 April 2018). "Within Decades, Floods May Render Many Islands Uninhabitable". National Geographic News. Archived from the original on 25 August 2019. Retrieved 25 August 2019.
  25. ^ Ngema, Thobeka (18 September 2023). "Several people injured after wave crashes into a restaurant at Marina Beach". IOL. Retrieved 24 October 2023.
  26. ^ Matthew Cappucci (25 January 2024). "Massive waves slammed a U.S. Army base. How it happened is mysterious". The Washington Post. Retrieved 26 January 2024.
  27. ^ Kinsman, Blair (1984). Wind Waves: Their Generation and Propagation on the Ocean Surface. Dover Publications. p. 10. ISBN 9780486495118.
  28. ^ Pennington, Rosemary (15 January 2015). "Debating Globalization and the Ninth Wave". Indiana University. Archived from the original on 29 November 2019.
  29. ^ Massel, Stanislaw R. (1996). "4.6". Ocean surface waves: their physics and prediction. Singapore: World Scientific. pp. 192–200. ISBN 9789810221096.

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