Ocean movements can be classified into waves, tides, and currents.
∙ When the water on the surface of the ocean rises and falls alternately, they are called waves. Waves are formed when winds scrape across the ocean surface. The stronger the wind blows, the bigger the wave becomes.
∙ The rhythmic rise and fall of ocean water twice in a day is known as a tide. Tides may be high or low. It is high tide when water covers much of the shore by rising to its highest level. It is low tide when waterfalls to its lowest level and recedes from the shore. Tides are caused due to the strong gravitational pull exerted by the sun and moon on the earth's surface. High tides help in navigation and fishing. The rise fall of water due to tides is being used to generate electricity in some places.
∙ Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. The areas where the warm and cold currents meet provide the best fishing ground of the world. For example, seas around Japan and the Eastern Coast of North America.