The Hidden Dangers of Square Waves in the Ocean

Square waves, also known as cross seas, create mesmerizing checkerboard patterns on the ocean’s surface, but they pose significant risks to swimmers.

Nature’s beauty often hides hidden dangers, and square waves are a prime example. These captivating grid-like patterns form when two wave systems intersect at angles greater than 45 degrees or when wind-driven waves collide with swells moving in different directions.

The result is a visually stunning but hazardous ocean surface.

Square waves create powerful currents that can be treacherous for swimmers and difficult for vessels to navigate. The European Space Agency noted in 2010 that these conditions occur frequently in the ocean, particularly when multiple swell systems coexist. A 2004 study found that a significant percentage of ship accidents occurred in crossing sea states, highlighting the dangers square waves present.

One well-known location where square waves are observed is Île de Ré, off France’s western coast. Tourists can safely view this phenomenon from a lighthouse on the island, but entering the water during such conditions is highly dangerous.