In the open ocean, how do we determine the depth to which wave activity influences water movement?
As the water’s energy moves forward toward the shore and the depth decreases, the diameter of these circular patterns also decreases. When the diameter decreases, the patterns become elliptical and the entire wave’s speed slows. Because waves move in groups, they continue arriving behind the first and all of the waves are forced closer together since they are now moving slower. They then grow in height and steepness. When the waves become too high relative to the water’s depth, the wave’s stability is undermined and the entire wave topples onto the beach forming a breaker.