The coral reefs are made up of thousands of tiny animals called as polyps. These are related to anemones and jellyfish. It possesses a sac-like a body and an opening which is encircled by the stinging tentacles called as cnidae.
They use calcium and carbonate ions which are derived from the seawater to in order to make a hard, cup-shaped skeleton. It protects the soft and delicate body of the polyp.
