Coral: Coral, commonly perceived as a single organism, is actually made up of thousands of genetically identical individuals called polyps, each only a few millimeters large.

Varying in size and shape, they are found in tropical coastal waters where they form atolls (as in the Polynesian islands) or reefs (as in the case of Australia, with the Great Barrier Reef). These colonies, generally, are typical of very bright and warm waters and hardly endure both high temperatures and pollution which leads, in fact, to their death and, therefore, to their sedimentation.

They present the gastrovascular cavity with longitudinal radial septa alternating with tentacles