A sneaker wave (also known as a sleeper wave, or (in Australia) a king wave) is a disproportionately large coastal wave that can sometimes appear in a wave train without warning. The terminology is popular rather than scientific: there is no scientific coverage (or evidence) 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 rogue waves. One American oceanographer distinguishes "rogue waves" as occurring on the ocean and "sneaker waves" as occurring at the shore.
Because they are much larger than preceding waves, sneaker waves can catch unwary swimmers, waders, and even people on the beaches and ocean jetties, and wash them into the sea. 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, Baker Beach, and those that face the Pacific Ocean) (e.g. from Big Sur to the California–Oregon border), Oregon, and Washington in the Western United States. 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). Sneaker waves are common on the southern coast of Iceland, and warning signs have been erected at Reynisfjara and Kirkjufjara beaches, following three unrelated tourist deaths in recent[when?] years. King waves occur especially in Western Australia and Tasmania, where they can be a hazard for rock fishermen.
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. 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.
- Miller, Craig (22 October 2013). "What Makes 'Sneaker Waves' so Sneaky -- and Dangerous". KQED. Retrieved 13 July 2020.
- Ted Andersen (28 September 2018). "California's deadliest beach is in the Bay Area". San Francisco Chronicle. Retrieved 10 August 2020.
- 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.
- 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.
- "Sleeper waves have led to other drownings in Humboldt County beaches". San Francisco Chronicle. 24 October 2006. Retrieved 1 August 2020.
- "Rogue or Sneaker Waves". Mary Donahue. Retrieved 1 August 2020.
- "Dangerous Sneaker waves possible on Central Coast". KION5/46. 26 December 2019. Retrieved 1 August 2020.
- "Sneaker/High Waves and Log Rolls Can Be Deadly". National Weather Service. Retrieved 13 July 2020.
- "Safety Issues Associated with Beaches". National Park Service.
- "New Residents: Welcome to Newport" (PDF). Newport, Oregon Police Department. 17 April 2018. Retrieved 13 July 2020.
- "Cape Scott Provincial Park: Hiking". Retrieved 28 July 2020.
- "Hiking and Outdoor Safety". Retrieved 16 July 2020.
- "Dangerous Sneaker Waves". Retrieved 20 July 2020.
- "Giant wave crashes into Tofino resort's oceanfront" (video). 18 January 2018. Retrieved 13 July 2020.
- ""Terrible situation" at Iceland's Reynisfjara beach - security to be improved". Iceland Monitor. 12 January 2017. Retrieved 13 July 2020.
- "King wave almost claims more at Salmon Holes". ABC News (Australia). 12 May 2011. Retrieved 13 July 2020.
- Kinsman, Blair (1984). Wind Waves: Their Generation and Propagation on the Ocean Surface. Dover Publications. p. 10. ISBN 9780486495118.
- Pennington, Rosemary (15 January 2015). "Debating Globalization and the Ninth Wave". Indiana University. Archived from the original on 29 November 2019.
- Massel, Stanislaw R. (1996). "4.6". Ocean surface waves: their physics and prediction. Singapore: World Scientific. pp. 192–200. ISBN 9789810221096.
- on YouTube - Video of a sneaker wave off the Oregon coast