Waves are disturbances of the ocean's surface and can be seen at any beach. They are caused by the mechanical energy that has been transferred to the water from the wind blowing over its surface. It is thought that ripples play an important role in providing the surface roughness necessary for the wind to push or pull the water.
The size of a wave depends on three factors: the distance over which the wind blows across open water (the fetch), the strength of the wind, and the duration that the wind blows. The larger these factors, the larger are the waves. Not surprisingly, the largest wind waves occur on the open ocean.
Although waves are constantly in motion, they have definite measurable features. The crest is the highest part of the wave and the trough is the lowest. The distance between the crest and the trough is called the wave height, while the distance between two crests is called the wave length. The period of the wave is the time it takes for two consecutive waves to pass a particular point. Waves continue to grow, absorbing more and more energy from the wind, until the wave height becomes one seventh the size of the wave length. At this point, it topples over, forming white caps.