A sea-surface wave that has become so steep (wave
steepness of 1/7) that the crest outraces the body of the
wave and it collapses into a turbulent mass on shore or
over a reef. Breaking usually occurs when the water
depth is less than 1.28 times the wave height. Roughly,
three kinds of breakers can be distinguished, depending
primarily on the gradient of the bottom: a) spilling breakers
(over nearly flat bottoms) which form a foamy patch at the
crest and break gradually over a considerable distance;
b) plunging breakers (over fairly steep bottom gradients)
which peak up, curl over with a tremendous overhanging
mass and then break with a crash; c) surging breakers
(over very steep bottom gradients) which do not spill or
plunge but surge up the beach face. Waves also break in
deep water if they build too high while being generated
by the wind, but these are usually short-crested and are
termed whitecaps.