If you ever see the rare phenomenon known as square waves, also known as a cross-sea, in the ocean, get out immediately.

While most waves form parallel to the shore and break at the coastline, square waves form a checkerboard-like pattern in the water and are extremely dangerous, even more so than a regular rip current.

Apparently, these unique waves form when two seas meet or intersect, according to Surfer Today.

"The conditions are quite common in the ocean and occur when a windsea and a swell, or two swell systems, coexist," the European Space Agency explained.

It happens when a specific weather pattern occurs that causes the waves to form at different angles, therefore creating a square pattern when the two collide.

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But while square waves may look cool, especially from higher ground or captured by a drone, they are very dangerous.

Square waves are typically associated with extra-strong rip tides, which can quickly sweep people into the water and make it difficult to get out without help.

These waves are even strong enough to cause shipwrecks and boat accidents, not to mention being too strong for a surfer or swimmer to escape from.

The swells can surge up to 10 feet high.

From 1995 to 1999, square waves were solely responsible for a large percentage of shipwrecks, according to the European Space Agency (ESA).

Now, ships have a technology called Synthetic-Aperture Radar (SAR), which helps crews detect potentially dangerous wave patterns, but square waves are still a scary risk.

However, that doesn't mean many people aren't fascinated by the ominous waves.

Surfer Today reported that the best place to watch square waves is the Isle of Ré in France off the coast of La Rochelle, which has become a major tourist destination.

Square waves have also been spotted in the South Pacific and the Atlantic Ocean, and has been seen at New Zealand's Whangamatā Beach and in Lisbon, Portugal.

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