If you see square waves forming in the ocean, get out of the water immediately

If you see square waves forming in the ocean, get out of the water immediately. These captivating wave patterns, known as cross seas, occur when two wave systems intersect at angles greater than 45 degrees or when wind and swell push waves in different directions.

Despite their visual appeal, cross seas pose a significant threat to swimmers and ships.

The grid-like formations hide dangerous currents that can destroy ships and endanger swimmers. The unique water patterns are extremely challenging to navigate, making them hazardous for boaters. Many boating accidents and shipwrecks are attributed to cross seas.

The European Space Agency noted in 2010 that these conditions frequently occur when a windsea and a swell, or two swell systems, coexist. A 2004 study indicated many ship accidents happened in such sea states. This phenomenon is often seen along the west coast of France, particularly at Isle de Ré.