The bounding waves

Stand at the seashore, or a lakeside, on a windy day. Watch the waves as they rush in toward you. They seem to come rolling at you as if pushed by a giant hand. With a great hiss and a swirl of foam, they surge up onto the beach. Then, almost at once, the water flows back out again. Only a last few sparkles are left on the wet sand.

Waves are made by wind blowing along the top of the water. The water seems to be moving forward-but it really isn't! It only moves up and down. A cork floating on the water would bob up and down as a wave moved under it. Unless pushed by the wind or tide, it would stay in the same place. This is because the water in a wave does not move forward. Only the shape of the wave moves forward.

You can see this for yourself. Tie a length of rope to a tree or post. Then wiggle the loose end of the rope. You'll see a wave shape travel down the rope. But the rope stays in the same place.