Coral polyps secrete calcium carbonate that build their skeletal structure and grow colonies. When groups of coral colonies are well established, they form a reef, which can be classified as fringing, patch, atoll, or barrier.
The most common reef formations found around the world are ‘fringing’ reefs, which form close to shore are generally still attached to the coast. These coral reef habitats are shallow and exposed during low tide. The largest fringing reef in the world is found along Ningaloo Coast, on the western side of Australia.