These marine homes grow in warm shallow seas and are built by coral animals, or polyps, with softbodies and mouths that are ringed by stinging tentacles. The polyps construct thimble-shaped skeletons of lime stone around themselves. As the polyps grow upwards, they keep dividing in two. They leave their skeletons behind them, however, and fuse together to make coral reef.
adapted from: Time Warner discoveries library- Under the Sea