Coral reef A fringing reef forms around an extinct volcanic island as the island and ocean floor subsides. As the subsidence continues, the fringing reef becomes a barrier reef and ultimately an atoll reef. Darwin predicted that underneath each lagoon would be a bedrock base, the remains of the original volcano. Subsequent research supported this hypothesis. Darwin's theory followed from his understanding that coral polyps thrive in the tropics where the water is agitated, but can only live within a limited depth range, starting just below low tide. Where the level of the underlying earth allows, the corals grow around the coast
Lihou Reef National Nature Reserve Lihou Reef National Nature Reserve Lihou Reef National Nature Reserve is a former marine protected area covering an area of 8440 kmin the Australian Coral Sea Islands Territory that was incorporated into the new Coral Sea Commonwealth Marine Reserve in December 2012. Together with the Coringa-Herald National Nature Reserve, from which it is separated by about 100 km of open ocean, it forms the Coral Sea Reserves Ramsar Site, designated on 16 August 2002, listing it under the Ramsar Convention as a wetland of international importance. Lihou Reef and its cays were discovered by Lieutenant John Lihou, R.N., on 23