Here's how it works:

* Wave motion: The wave itself travels horizontally across the surface of the water.

* Particle motion: The water particles themselves don't travel with the wave. Instead, they move in a circular path, up and down and slightly back and forth.

* The circle: The diameter of the circle the particles move in decreases as you go deeper into the water. At the bottom, there is essentially no motion.

Think of it like this: Imagine a floating buoy in the ocean. As a wave passes by, the buoy will bob up and down, and slightly back and forth, in a circular path. This is the motion of the water particles as well.

Important Note: This is true for surface waves, which are the kind we most often see on the ocean. There are other types of waves in water (like internal waves or tsunami waves) where the particle motion might be different.