A sneaker wave, 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, washing them out to sea. It is not uncommon for people walking or standing on beaches and ocean jetties to also be washed into the sea. Sneaker waves are mainly referred to in warnings and reports of incidents for the coasts of Northern California, Oregon and Washington in the United States. These sneaker waves also occur on the west coast of Canada, they are commonly seen in Tofino and Ucluelet. Sneaker waves are common on the southern coast of Iceland, and warning signs have been erected at Reynisfjara and Kirkufjara beaches, following three unrelated tourist deaths in recent years. King waves occur especially in Western Australia and Tasmania.
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.
- ""Terrible situation" at Iceland's Reynisfjara beach - security to be improved". Iceland Monitor. Retrieved 23 December 2017.
- See the external links
- Kinsman, Blair (1984). Wind waves : their generation and propagation on the ocean surface. Dover Publications. p. 10. ISBN 0-486-49511-6.
- Rosemary Pennington. Debating Globalization and the Ninth Wave. University of Indiana, "Framing the Global" program debate
- For example: Massel, Stanislaw R. (1996). Ocean surface waves: their physics and prediction. Singapore: World Scientific. ISBN 981-02-2109-6. §4.6, pp. 192–200.
- National Park Service US Department of the Interior warning page
- Oregon Parks and Recreation Department warning page
- Washington State Department of Ecology warning page
- King wave almost claims more at Salmon Holes article about a nearly fatal incident
- Sneaker wave off the Oregon coast Video of a sneaker wave off the Oregon coast