Most of the damage in coastal areas is due to wave action. Between one third and one half of all the beaches in Florida are eroding at the present time. This threat has been sufficiently severe for the state to enact comprehensive coastal legislation. Most waves are small (a few feet), but some reach heights in excess of 100 feet (30m). Waves are generated by the friction between air and water; and their size is a function of wind speed, duration, and fetch (the distance over which the wind blows). 

In open water, waves have little effect on the ocean bottom because there is no forward motion of the water. When water depth equals one half the wavelength, the waves begin to interact with the bottom and slow down. If the approaching waves are not parallel to the beach, the leading portion of the wave front will slow down first. As a consequence, the wavefront will bend (refract) and tend to line up parallel to the beach. Because of refraction, wave energy tends to concentrate on headlands. 

As water depth becomes even shallower, the waves will steepen and begin to break in the surf zone. Breakers then interact with the beach, geologically defined as that portion of the shore which extends from the low tide line to the highest area of wave action. As with most geological processes, day-to-day changes are virtually imperceptible. Only during storms are changes quite rapid and noticeable.