Undulations of the ocean surface, generally
the result of the action of wind on the water surface. At sea, there is
no overall translational movement of the water particles: they move up and
forward with the crest, down and backward with the trough with the trough,
describing a vertical circle. Near the shore, friction with the bottom causes
increased wave height, and the wave breaks against the land. Waves thus
cause much coastal erosion.