If you’ve ever played in the ocean, chances are you’ve been knocked down by a wave or two. Waves on the surface of the ocean are usually caused by wind. The wind gives energy to the water, and the energy travels through the water in the form of waves. Damaging waves can be stirred up by heavy winds and storms, and earthquakes or volcanic activity near or under the ocean can cause large tsunamis. Waves can be all shapes and sizes, depending on wind speed and the “fetch” of the wave. The fetch refers to the size of the area over which the wind is blowing. In general, the larger the fetch, the larger the wave.