This coral reef is composed mainly from starlet corals. Starlet coral (Siderastrea siderea) forms rounded heads or boulders up to 4 feet (1.2 meters) in diameter. The surface of the coral is covered with tiny coral polyps. The individual coral polyps create a colony and secrete calcium carbonate to form a hard skeleton structure. Over thousands of years, these hard structures build up to form a reef. Once lone gorgonian coral can be seen growing like a tree in the center of the image.