The answer is:

Waves usually run parallel to the shore, but a cross sea is different. It happens when opposing swells collide. The waves of the newer weather system run at an oblique angle to the old weather system, whose waves continue despite the wind shift, when the wind from two weather systems—one old and the other more recent—meet.

Although rare, the event is very harmful. From above, it appears as though an underwater grid is creating square-shaped ripples in these waves.

If you hike to the top of a cliff or lighthouse or fly a drone over the region, you can clearly identify the odd pattern.

Nevertheless, no situation occurring beneath the ocean produces square waves. Rather, they are the outcome of the water’s flow.