Coral are colonial invertebrate marine animals whose skeletons help to build up reefs.
Corals are relatives of animals like jellyfish, but unlike them, corals are not free swimming. Coral reef ecosystems are some of the most productive, diverse, complex and beautiful places on earth. The total number of coral species that live in the reefs of the Hawaiian Islands is relatively low. Scientists think that this is because of the isolation of the Hawaiian Islands. On the other hand, because of this isolation, a number of coral species live nowhere else on earth.