Winds blowing across the surface of the world's oceans transfer massive amounts of kinetic energy to the water. This energy is visible as waves. The total amount of power released by waves breaking along the world’s coastlines has been estimated at 2 to 3 million megawatts, equivalent to the output of 3,000 large conventional power plants.

The size of a wave depends on the wind's speed and fetch, i.e., the unimpeded distance over the ocean’s surface that the wind blows.

Figure 12 Fetch Wave size depends on the wind speed and the distance the wave travels. Source: National Oceanic and Atmospheric Administration