Many people think of coral as hard, rock-like formations that attract abundant, diverse marine life. In fact, corals are themselves tiny marine animals called polyps that live together in large colonies.
Coral polyps are relatives of jellyfish and anemones. Some live in shallow water, some in deep; some form hard outer skeletons made of calcium carbonate, others have a soft body encasing hard internal structures known as sclerites. Hundreds of thousands of hard corals with their skeletons glued together form the iconic reef structures that do, indeed, serve as the foundation for important marine ecosystems around the world.