Those waves hitting the sand actually begin far out at sea. And it doesn’t take much to get them going. A little wind will do the trick. First the wind blows over the surface of the water, generating the little ripples you can see just by blowing across a panful of water. If that’s all that happens, the ripples merely shimmer around on the surface. But a stronger wind can cause these little ripples to merge with other ripples and become larger. Eventually these combinations grow large enough to become what most folks would call a wave. Small waves have the ability to combine with other waves that have a similar frequency. “Frequency” here just means the time it takes for the crest of a wave to pass and the next one to take its place. It’s pretty much a coincidence when one wave happens to meet another that matches its frequency. But once you have a match, the two combine to form a single, larger wave. Just keep up this process to see how even a moderate amount of wind can make waves.