Coral reefs cover about 300,000 square km of the world’s Shallowmarine areas, growing gradually as the organisms forming their living surfaces multiply, spread, and die, thus adding their limestone skeletons to the reef. A good way to imagine a coral reef is to think of it as a bustling city or community, with the buildings made of coral, and thousands of inhabitants coming and going, carrying out their business. In this sense, a coral reef is like a metropolis under the sea. The adaptation to the environment in which reef inhabitants live has led to development of the most amazing mechanisms of survival, extraordinary symbiosis and astonishing mimicry. Nowadays one of the most important issues for the whole planet is to save this beautiful world from destruction.