Coral reefs form some of the most diverse ecosystems on earth. They occupy less than 1% of the worlds ocean surface, about half the area of France, yet they provide a home for 25% of all marine species, including fishes, molluscs, echinoderms and sponges. They are most commonly found at shallow depths in tropical waters, particularly in the Pacific Ocean. Coral reefs deliver ecosystem services to tourism, fisheries and shoreline protection. The annual global economic value of coral reefs has been estimated at $375 billion. It is believed to have emerged more than 540 million years ago. New species originate 50% faster in coral reefs than in any other habitats. The fossil records show that reefs have been remarkably successful in surviving through large environmental disturbances. However the combination of drastic environmental changes that we're seeing today, such as degraded water quality, depleted fish stocks, coral bleaching, ocean acidification and loss of habitat causes them to be under great threat. Coral reefs are perhaps one of the greatest but, least known of wonders of our world. There are three different kinds of coral reefs. There are fringing, barrier, and atoll. Fringing reefs are attached to margins of an island or continent, rough, table like surface, as much as 1 kilometer wide. On their seaward side they slope steeply to the ocean floor. Fringing reefs grow in shallow water near the shore and prefer dry climates with limited river runoff. There are also barrier reefs, which are similar to fringing but separated from mainland with a lagoon The most popular barrier reef is the Great Barrier Reef in Australia, which spans over 2,000 kilometers. The third type of coral reef is the atoll. Atolls consist of a continuous or broken ring of coral reef surrounding a central lagoon. Atolls are unique because they reach to depths of thousands of