<P> Breaking of water surface waves may occur anywhere that the amplitude is sufficient, including in mid-ocean . However, it is particularly common on beaches because wave heights are amplified in the region of shallower water (because the group velocity is lower there). See also waves and shallow water . </P> <P> There are four basic types of breaking water waves . They are spilling, plunging, collapsing, and surging . </P> <P> When the ocean floor has a gradual slope, the wave will steepen until the crest becomes unstable, resulting in turbulent whitewater spilling down the face of the wave . This continues as the wave approaches the shore, and the wave's energy is slowly dissipated in the whitewater . Because of this, spilling waves break for a longer time than other waves, and create a relatively gentle wave . Onshore wind conditions make spillers more likely . </P> <P> A plunging wave occurs when the ocean floor is steep or has sudden depth changes, such as from a reef or sandbar . The crest of the wave becomes much steeper than a spilling wave, becomes vertical, then curls over and drops onto the trough of the wave, releasing most of its energy at once in a relatively violent impact . A plunging wave breaks with more energy than a significantly larger spilling wave . The wave can trap and compress the air under the lip, which creates the "crashing" sound associated with waves . With large waves, this crash can be felt by beachgoers on land . Offshore wind conditions can make plungers more likely . </P>

Force of sea waves as they break against coastline is known as