Square Waves Are Real – And Can Kill You In An Instant

Wikimedia Commons / Michel Griffon

Summer is the perfect time to hit the beach, or go out for a nice evening boat ride. Maybe you’re even romping around in the marina on waterskis or zooming around the bay on a jet ski – but if you see this one pattern appear in the water…you need to get out as fast as possible.

Anyone who’s ever seen a move where a ship capsizes in a dramatic fashion (think The Perfect Storm) knows the end result of terrible waves and problematic sea currents.

This is exactly what can happen if you start to see square waves appear in the water.


The appearance of square waves is commonly called a “Cross Sea” and the phenomenon forms when water waves intersect with waves created by a separate weather system – usually, strong winds.

A cross sea is known to have a large amount of directional spreading and usually only last until the older weather system stops affecting the ocean and allows the new one to create the wave direction.

Called a “perilous sea hazard” a cross sea can affect boats, watercraft, and swimmers alike. Farther from the shore, the danger becomes much greater as the waves are often larger and more powerful.


Closer to shore, the waves can create deep and forceful rip currents that can drag you underneath a wave and pull you in multiple directions at one time – preventing you from being able to get back to the surface.

Cross seas are credited with the death of many seafaring people and tragic shipwrecks. While ships are made to withstand strong waves, when you have two different waves, it can easily put the vessel in a dangerous and deadly situation.

Watch this video below that talks all about this natural phenomenon.