Waves are the raised swells of water that move along the surface of the ocean. At the beach, surfers ride on the waves:
The size of the waves depends on the general movement of the ocean water in the area, the shape of the sea floor, and whether there are storms or strong winds that can produce bigger waves.
The word tide refers to the variation in the general level of the ocean. Tides are caused by the gravitational forces of the moon and sun, as well as the rotation of the earth. Many places have one or two times of high tide and low tide per day: