Waves erode the beach in several ways: by impact, from the sheer mass of the water being hurled at the coast; by the lifting action of turbulent water; by hydraulic pressure, whereby the onrushing water compresses the air in the cracks in rocks and when the waves retreat there is a sudden pressure drop (very much like the hammering of water pipes with air in them); and by abrasion, by which waves pick up bottom sediments and blast the coastline with them. More subtle is the chemical action of seawater, which weathers certain minerals, and the action of living things such as rock-boring clams, all of which increase erosional rates. 

Erosion is most severe where shorelines are composed of loose sediments and during times of extreme conditions, such as those associated with seismic waves (tsunamis) or hurricanes. In the latter case, huge waves, especially when combined with high tides and the bulge in the sea associated with the low pressure center of the storm, may devastate enormous areas and restructure coast lines in novel ways. 

Each beach represents a unique set of local conditions where the atmosphere, the hydrosphere, and the lithosphere interact in dynamic fashion. The sediments removed by erosion will travel along the beach in two ways: as beach drift and as longshore drift. Beach drift is due to the wash and swash action of waves. An incoming wave will carry a sand grain up the beach at a slight angle. This same grain will be carried straight out because the return swash is being pulled by gravity. Continuous wave action thus moves the sand grains along the beach. This same zig-zag motion of the water also creates a current called the longshore current which runs parallel to the beach and carries sediment just outside of the inner surf zone. Sediments are also moved outward from the beach to deeper water by rip currents and by tidal flow from inlets and estuaries. The beach can best be thought of as a continually moving blanket of sand, where every portion of the beach is dependent on evry other portion to maintain itself.