There are two types of surface waves: seas and swells. Seas refer to short-period waves still being created by winds. Swells refer to waves that have moved out of the generating area. In general, swells are more regular waves with well-defined long crests and relatively long wave periods.
The growth of wind-generated oceanic waves is not indefinite. The point when waves stop growing is termed a fully developed sea condition. Wind energy is imparted to the water leading to the growth of waves; however, after a point, the energy imparted to the waters is dissipated by wave breaking. Seas are short-crested and irregular and their periods are within the 3- to 25-second range.
Seas usually have a shorter period and length and their surface appears much more disturbed than that found on swells. Waves assume a more orderly state with the appearance of definite crests and troughs when they are no longer under the influence of winds (swell).