Waves are formed everywhere on the sea or for that matter on any large water body. There are two physical mechanisms that control and maintain waves. For most waves, gravity is the restoring force that displaces the surface to be accelerated back towards the mean surface level. The kinetic energy gained by the fluid returning to its rest position causes it to overshoot, resulting in the oscillating wave motion.
In the case of ripples, the restoring force is surface tension, wherein the surface acts like a stretched membrane. Waves on sea surface are generated by the action of the wind.
The height of simple waves is the elevation difference between the top of a crest and the bottom of a trough. The height of wind waves increases with increasing wind speed and with increasing duration and fetch of the wind. Together with height, the dominant wavelength also increases. Finally, however, the waves reach a state of saturation, because they attain the maximum significant height to which the wind can raise them, even if duration and fetch are unlimited.
After becoming swell, the waves may travel thousands of kilometers, particularly if the swell is from the great storms. In travelling, the swell waves gradually become lower; energy is lost by internal friction, air resistance and by energy dissipation because of divergence of the directions of propagation.
When waves run into shallow water, their speed of propagation, height and wavelength decrease. In the final stage, the shape of the wave’s changes, and the crests become narrower and steeper until, finally, the waves become breakers (surf). Generally, this occurs where the depth is 1.3 times the wave height.