When you think of the ocean you probably picture the waves breaking against the shore.  Come to think of it, no matter when you go, the waves are rolling in. The ocean doesn't seem to take a break.

What's causing that?

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.

Waves

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.