Billions of colorful algae, called zooxanthellae, that live in symbiosis with corals, are responsible for the beautiful colors of the coral reefs.<br />There are three type of coral reefs: barrier reef, fringing reef and atolls. Barrier reef is usually located in deep water, away from the shore. Fringing reef is fringe-shaped and located in the shallow water. Atolls are island-shaped. They grow on the edges of the lagoons.
