Found in shallow tropical marine waters, the underwater coral reef is a aragonite structure produced by living organisms. Because of the extreme conditions in these waters, algae and other similar plants do not grow, allowing the predominant organisms to be corals. These are colonial cnidarians that secrete an exoskeleton of calcium carbonate( limestone). The pilling up of this skeletal material produces a massive calcareous formation that supports the living corals and a large diversity of animals and plant life. Depending on the form and the water depth, the underwater coral reef can take various forms. The first form is the apron underwater coral reef.
This type of coral is rather short and very sloped, going directly downward from the peninsular shore. The fringing underwater coral reef is probably the most common type . This type is directly connected to a shore or borders it with a shallow channel or lagoon. The barrier underwater coral reef is the type of coral reef that is separated from a mainland or island shore by a deep lagoon. The patch underwater coral reef type is rather isolated, often found in a circular form found usually in a lagoon or embayment. The ribbon underwater coral reef type is the long, narrow, winding reef, that is usually found in a atoll lagoon. The atoll underwater coral reef is a more or less circular and continuous barrier reef. The particular thing about this type of underwater coral reef is that it extends all around a lagoon, without a central island. The bank reef is last type of underwater coral reef. The bank reef us a linear or semi circular in outline and is larger then the patch reef. Underwater coral reef is mostly found in the Indian and Pacific oceans, counting for about 92% of the total worldwide surface covered by coral reef.
