The term 'Reef Type' can refer to a type of CORAL reef. CORAL reefs are large underwater structures composed of the calcium carbonate skeletons of marine organisms, such as corals and other invertebrates. They are found in warm, shallow waters of tropical oceans and provide habitats for a wide variety of marine life. CORAL reefs are also important sources of food and shelter for many species of fish, mollusks, and crustaceans.