If You Ever See “Square Waves” in the Ocean — Get Out Immediately
Nature never stops amazing us. From breathtaking sunsets to towering mountains, it has endless wonders.
But some of the most fascinating sights can also be the most dangerous — like the rare and mesmerizing “cross seas” (also called square waves).
These striking, chessboard-like patterns appear when two different wave systems collide at angles greater than 45° — often caused by wind pushing waves in one direction while a swell pushes in another.
The result? A hypnotic grid across the ocean’s surface that looks like art… but hides a serious danger.
Beneath these patterns are powerful, unpredictable currents that can pull swimmers under and make it almost impossible for boats to steer.
Waves in cross seas can reach heights of up to 10 feet, and sudden shifts in wind patterns can make the situation worse.
The European Space Agency notes that cross seas are more common than most people think, and studies have linked them to a significant number of shipwrecks and boating accidents.
Along the western coast of France, near Île de Ré, tourists often spot them from a safe distance — usually from the island’s lighthouse — because entering the water during this phenomenon can be deadly.
Rule of Thumb: If you see perfect square-like wave patterns forming in the ocean, do not swim, surf, or sail. Stay onshore and admire nature’s beauty from a safe spot.
Watch the incredible footage of this natural phenomenon in the video below — and share this with friends and family so they know the hidden danger behind these picture-perfect waves.
