The ocean covers two-thirds of the Earth's surface. This vast body of water is home to a great variety of plants and animals. On the ocean floor, there are underwater mountain ranges, plains covered with clays and mud like oozes, deep trenches, and submerged mountains called sea mounts. Animals live in all of these regions and in all depths of the ocean. Plants are restricted to the sunlit waters near the surface. Ocean wildlife is at its richest in the warm, shallow waters of coral reefs.