The total area of coral reef in India is estimated to be about 2,375 km2 which is less than 1 % of all the coral reef areas in the world. Hard corals are commonly referred to as "reef builders" due to the calcium carbonate skeletons they secrete. Soft corals are octacorallia while hard corals are hexacorallia. Corals reproduce sexually by either internal or external fertilization. Hermatypic corals are known to harbour Zooxanthellae in their body wall. Urban and industrial waste, sewage, agrochemicals, and oil pollution are poisoning reefs. Crown-ofthorns starfish (Acanthaster planci) is an echinoderm is a main predator for coral polyp. Warmer water temperatures can result in coral bleaching.