Large and Dangerous Waves: Meteotsunamis, Sneaker Waves, the Biggest Waves Ever | Sea Life, Islands and Oceania

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LARGE WAVES

Rockall wave in March 1943

Large waves are caused by a number of factors. The largest ones that occur with some consistency are caused by large storms far at sea. These waves are remarkable more for their vertical height rather the amount of water moved, which is the case with tsunamis, which can bring great amounts of water far inland. The Indian Ocean tsunami in December 2004 traveled at speeds reaching 500 miles per hour and surged up to 1.6 kilometers (a mile) inland. It killed some 220,000 people, making it the deadliest wave known.

Waves with a large vertical height often begin as smaller waves have a chance to build up and combine into large waves. They break when the waters gets shallow and the wind blows off the land and pushes them up some.

The huge waves in Hawaii are created by intense wintertime low-pressure systems that produce of succession of storms that generate huge ground wells that roll 1,500 miles across the north Pacific. One reason waves are so big in Hawaii is that the Hawaiian islands lack a continental shelf which slows the momentum of waves.

Large waves are thought to form from swells in the ocean.Elizabeth Rayne of SYFY wrote: Swells are groups of waves powered by furious storm winds far from land, but can travel thousands of miles to the shore. They travel in different directions and at different speeds, and when they collide, they pass right through each other and form enormous waves that rear their frightening heads but vanish in seconds. Swells going in the same direction can end up forming behemoths that last for minutes. Even the larger waves that occur because of swells are nothing compared to rogue waves (See Below). [Source: Elizabeth Rayne, SYFY, March 9, 2022]

In 2007, large waves swamped houses and damaged building and fighing boats in western Indonesia and southern Thailand. Similar damage was reported more than 6,000 kilometers away in Mauritius. The waves are believed to have been from the same storm, traveling thousands of kilometers after being created a storm off South Africa. [Source: Earth Observatory, May 2007]

Websites and Resources: National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org

Tsunamis

A tsunami is a series of waves produced by an event in the ocean such as an underwater landslide, volcanic eruption or an earthquake that cases large amounts of seawater to be displaced . Sometimes they can be very large. Catastrophic ones occur a few times a century, Other times they are so small they virtually undetectable. For a long time tsunamis were erroneously called tidal waves. The word tsunami is derived from the Japanese “tsu” (“harbor”) and “nami” (“waves”).

Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel inland, they build up to higher and higher heights as the depth of the ocean decreases. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves. [Source: NOAA]

Biggest Waves in Recorded History — Earthquake-Landslide-Caused Tsunamis

Lituya Bay megatsunami diagram

The largest known vertical wave in recent times was over 30 meters (100 feet) tall. It occurred in July 1958 and was produced by a tsunami caused by an earthquake-induced a landslide in Alaska’s Lituya Bay. When the wave ran ashore, it snapped trees on a mountain 524 meters (1,719 feet) upslope from at the entrance of Gilbert Inlet. Five deaths were recorded, but property damage was minimal because there were few people living in th area and no cities or towns nearby.

The magnitude of the 1958 Lituya Bay was 7.8 to 8.3. The landslide contained 30 million cubic meters (40 million cubic yards) and about 90 million tons of rock and soil and vegetation into the narrow inlet of Lituya Bay. The impact was heard 80 kilometers (50 mile) away,[7] and the sudden displacement of water resulted in a megatsunami that washed out trees to a maximum elevation of 524 meters (1,719 feet). The enormity of the disaster resulted in a re-evaluation of large-wave events and the recognition of impact events, rockfalls, and landslides as causes of very large waves. In the past 150 years Lituya Bay has had three other tsunamis over 30 meters: 1854 120 meters or (395 fee), 1899 (61 meters of 200 feet), and 1936 (150 meters or 490 feet).[Source: Wikipedia]

Of the five 5 people killed, two people from a fishing boat died as a result of being caught by a wave in the bay. Two others, a fishing boat captain and his seven-year-old son, were struck by the wave and lifted over 100 meters feet into the air by the swell but survived more or less unhurt. Yakutat, the only permanent outpost close to the epicenter at the time, sustained damage to infrastructure such as bridges, docks, and oil lines.

Unzen, a large volcano on Kyushu near Nagasakai, erupted catastrophically in 1792. An earthquake triggered by the eruption and the collapse of a lava dome sent an entire mountain side sliding into the ocean. The ensuing 100-meter-high tsunami submerged coastal villages, killing about 15,000 people. Tsunamis engulfed the city of Shimabara with water reaching as far inland as the gates of the city castle. More than 43 square miles of the Shimabara peninsula was covered by water. The waves then traveled across the bay, washing away nearly 6,000 houses and 1,600 fishing boats along another 75-miles section of coastline.

Meteotsunamis

Meteotsunamis are large waves caused by storms. Unlike tsunamis triggered by seismic activity, meteotsunamis are driven by air-pressure disturbances often associated with fast-moving weather events, such as severe thunderstorms, squalls, and other storm fronts. The storm generates a wave that moves towards the shore, and is amplified by a shallow continental shelf and inlet, bay, or other coastal feature. [Source: NOAA]

Damage from the 1958 Lituya Bay megatsunami in an aerial photograph of Lituya Bay, The lighter areas at the is where shore where trees have been stripped away. The red arrow shows the location of the landslide, and the yellow arrow shows the location of the high point of the wave sweeping over the headland.

Meteotsunamis have been observed to reach heights of two meters (6 feet) or more. They occur in many places around the world, including the Great Lakes, Gulf of Mexico, Atlantic Coast, and the Mediterranean and Adriatic Seas.

Identifying a meteotsunami is a challenge because its characteristics are almost indistinguishable from a seismic tsunami. It can also be confused with wind-driven storm surge or a seiche. These uncertainties make it difficult to predict a meteotsunami and warn the public of a potential event. However, NOAA scientists have identified atmospheric conditions that are likely to generate a meteotsunami and continue to work on ways to forecast them.

Seiches (See Below) and meteotsunamis are often grouped together, but they are two different events. Winds and atmospheric pressure can contribute to the formation of both seiches and meteotsunamis; however, winds are typically more important to a seiche motion, while pressure often plays a substantial role in meteotsunami formation. Sometimes a seiche and a meteotsunami can even occur at the same time. Seiches are standing waves with longer periods of water-level oscillations (typically exceeding periods of three or more hours), whereas meteotsunamis are progressive waves limited to the tsunami frequency band of wave periods (two minutes to two hours). Seiches are usually limited to partially or fully enclosed basins, such as Lake Erie. Meteotsunamis can occur in such basins but are also prevalent on the open coast. A single meteotsunami can travel long distances and influence a very large range of the coastline.

Seiche

Similar in motion to a seesaw, a seiche is a standing wave in which the largest vertical oscillations are at each end of a body of water with very small oscillations at the "node," or center point, of the wave. Standing waves can form in any enclosed or semi-enclosed body of water, from a massive lake to a small coffee cup.[Source: NOAA]

If you have observed water sloshing back and forth in a swimming pool, bathtub, or cup of water, you may have witnessed a small-scale seiche (pronounced saysh). On a much grander scale, the same phenomenon occurs in large bodies of water such as bays and lakes. A seiche may occur in any semi- or fully-enclosed body of water.

Seiches are typically caused when strong winds and rapid changes in atmospheric pressure push water from one end of a body of water to the other. When the wind stops, the water rebounds to the other side of the enclosed area. The water then continues to oscillate back and forth for hours or even days. In a similar fashion, earthquakes, tsunamis, or severe storm fronts may also cause seiches along ocean shelves and ocean harbors.

Lake Erie is known for seiches, especially when strong winds blow from southwest to northeast. In 1844, a 22-foot seiche breached a 14-foot-high sea wall killing 78 people and damming the ice to the extent that Niagara Falls temporarily stopped flowing. As recently as 2008, strong winds created waves 12 to 16 feet high in Lake Erie, leading to flooding near Buffalo, New York. Lake Pontchartrain, Louisiana, is also known to routinely form small seiches after the passage of afternoon squall lines during summer months. In some of the Great Lakes and other large bodies of water, the time period between the "high" and "low" of a seiche can be as much as four to seven hours. This is very similar to the time period between a high and low tide in the oceans, and is often mistaken as a tide.

Rogue Waves

Rogue wave in the Bay of Biscayne in 1940

Massive waves, called freak waves, killer waves or rogues, develop in the open sea and are a serious danger to even the largest ships. Between 1984 and 2004 more than 200 super carriers were lost at sea, reportedly due to massive waves. These waves can reach heights of over a 30 meters 100 (feet) and generate a force equal to 100 tons a square meter. They are a threat to cargo ships and ocean liners. Such waves can also be a threat to coastal communities and beachgoers if they make it all the way to shore.

Rogue, freak, monster or killer waves have been part of marine folklore for centuries and were thought to be myths or exaggerations. They have only been accepted as real by scientists over the past few decades. The Draupner wave, a single giant wave measured on New Year's Day 1995 on an oil platform the North Sea, finally confirmed the existence of rogues. This wave had reached a height of 25.6 meters (84 feet). Careful analysis of two European Space Agency satellite images of the world’s oceans over a three week period in 2001 scientists spotted ten waves that were over 25 meters (82 feet) in height, indicating that not only do they exist but occur with more frequency than people had thought.

Rogues, called 'extreme storm waves' by scientists, are those waves which are greater than twice the size of the highest surrounding waves, are very unpredictable, and often come unexpectedly from directions other than prevailing wind and waves. They are often described by witnesses as "walls of water". They are often steep-sided with unusually deep troughs.[Source: NOAA]

Alaskan Waves Break Apart a Giant Antarctic Iceberg, 13,500 Kilometers Away

A bad storm in Alaska in October 2005 generated an ocean swell that broke apart a giant iceberg near Antarctica six days later. Reuters reported: The waves traveled 13,500 kilometers (8,300 miles) to destroy the iceberg, said Douglas MacAyeal of the University of Chicago and Emile Okal at Northwestern University. Writing in the journal Geophysical Research Letters, they said their study shows how weather in one region can affect events far away. [Source: Reuters, October 3, 2006]

“The researchers were watching icebergs using satellite images, and saw that on a clear, calm day last October, a big iceberg known as B15A broke into half a dozen pieces. MacAyeal and colleagues had put seismometers and other instruments on the 60-mile-long (100-kilometer-long) iceberg and on Antarctica’s Ross Ice Shelf. “We are trying to figure out how the icebergs are sort of making music when various phenomena that we think are linked to the cracking of iceberg masses takes place,” Okal said.

“So when they saw B15A break up, they persuaded other researchers in Antarctica to fly over to the beg and get their instruments. The seismometer record showed that although it was mild and clear, the iceberg had been moving up and down and from side to side. “I was surprised at the level of amplitude that we were recording,” Okal said. The researchers figured a storm somewhere may have generated waves, which are known to travel long distances.

They did some calculations and saw the swell must have come from more than 13,500 kilometers away. “Our jaws dropped,” MacAyeal said. “We looked in the Pacific Ocean and there, 13,500 kilometers away, six days earlier, was the winter season’s first really big, nasty storm that developed and lasted for about a day and a half in the Gulf of Alaska.”

They looked at records from wave buoys in between. “We saw that the waves in Alaska were about 35 feet (10 meters) tall and then two days later they were down to 15 feet (4.5 meters) as they passed Hawaii on their way south,” MacAyeal said. And three days later, a sensitive seismometer on Pitcairn Island in the south Pacific recorded the waves’ passage. “We think that B15A was in the right position where these waves would be fatal to it,” MacAyeal said. “The iceberg shattered like a gracile wine glass being sung to by a heavy soprano.”

Sneaker Waves Kill Three People at Big Sur California

A sneaker wave, also called a sleeper or king wave, is a sudden, powerful surge of water that travels farther up the beach than expected. It often catches people off guard. These waves can knock people down and drag them into the ocean. This is extremely dangerous and can lead to drowning due to cold water immersion and rip currents. Sneaker waves appear unexpectedly and can occur even on days with calm-looking surf, so it is critical to practice beach safety, especially on coastlines prone to them, such as the Pacific Northwest, northern California and parts of Australia.

In November 2025 there were two incidents involving sneaker waves that killed people at Garrapata State Park in the Big Sur area of California. In the first incident, 39-year-old Yuji Hu of Canada and his 7-year-old daughter died after being swept into the ocean during by 15 to 20 foot waves. The girl was swept away first and her father died while trying to rescue her. The girl’s mother also entered the water in an attempt to save them but survived. [Source: Jack Dolan, Los Angeles Times, November 24, 2025; Warren Pederson, San Francisco Chronicle, November 23, 2025]

A week or so later, high surf and sneaker waves swept three people—two women and a man—off the rocks at Soberanes Point. The women managed to reach shore and were hospitalized with unspecified injuries, but the man, about 30 years old and wearing a white turban, died.

The man was initially missing. Multiple agencies—including California State Parks, the Monterey County Sheriff’s Office, Cal Fire, CHP, and the U.S. Coast Guard—conducted an extensive search using boats, divers, and helicopters. A Coast Guard helicopter briefly spotted what appeared to be a body, but lost visual due to the dangerous surf, with waves reaching 13–18 feet. The search was halted at nightfall and resumed the next morning.

Authorities warned beachgoers to stay off rocks and away from the water’s edge due to powerful surf, rip currents, and unpredictable sneaker waves. Recovery crews have described responding to nearly identical tragedies within eight days as extremely difficult.

Sneaker Waves Kill Two in North Carolina

Two separate tragedies on the North Carolina coast highlight the danger of strong surf and unexpected waves. Both incidents involved unexpected waves and hazardous surf, underscoring the risks of walking near the water’s edge even in seemingly moderate conditions. [Source: Emily Shapiro, ABC News, July 17, 2019; Nicole Rojas, Newsweek, April 30, 2018]

In July 2019, at Wrightsville Beach, 35-year-old father Johnny Lee Vann Jr. died while trying to save his children after a wave swept them off a jetty wall. Vann managed to reach one child, but when he went back into the rough water for the second, he was pulled under. Bystanders rescued both Vann and the child, but despite CPR, he could not be revived. His wife described him as a devoted husband and father.

In April 2018, the body of 4-year-old Wesley Belisle of New Hampshire was found on Carova Beach after being swept out to sea by a rogue wave days earlier in Kitty Hawk. The boy disappeared while walking along the shore with his mother. Despite an extensive Coast Guard search covering 130 square nautical miles, he was not found alive. His body eventually washed ashore roughly 34 miles from where he was swept away.

Sneaker Waves Kill Six in Australia

A powerful run of storms and large swell on Australia’s east coast triggered a series of deadly accidents, with at least six people killed and several others swept into the ocean over the Easter weekend. A widely shared video captured a man at Sydney’s northern beaches being swept away by a rogue wave while watching the giant surf at Dee Why. [Source: Dashel Pierson, Surfer Magazine, April 19, 2025; [Source: Cooper Gegan, The Inertia, April 21, 2025]

In Victoria, a group standing on coastal rocks near Punch Bowl Road was hit by heavy waves. One woman drowned, another woman survived, and a man remains missing. New South Wales saw multiple Good Friday drownings: 1) a fisherman washed off the Wollongong Harbor breakwall; 2) a person who fell or was swept into Sydney Harbor; and 3) and another victim who drowned at Green Cape on the far south coast.

According to national reports, five people died in NSW and one in Victoria, with two others missing, all believed to have been swept into the ocean while fishing or walking on rocks. The massive swell—generated by a Tasman Sea low-pressure system—delivered historic surf at big-wave spots like Cape Solander and Deadman’s, drawing crowds but prompting warnings. Surf Lifesaving NSW urged the public to stay off closed beaches and avoid unnecessary risks as strong surf and sneaker waves continued to batter the coastline.

Image Sources: Wikimedia Commons; YouTube, NOAA

Text Sources: National Oceanic and Atmospheric Administration (NOAA) noaa.gov; “Introduction to Physical Oceanography” by Robert Stewart , Texas A&M University, 2008 uv.es/hegigui/Kasper ; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated November 2025