Coral reef to form fringing reefs, and can eventually grow become a barrier reef. Where the bottom is rising, fringing reefs can grow around the coast, but coral raised above sea level dies. If the land subsides slowly, the fringing reefs keep pace by growing upwards on a base of older, dead coral, forming a barrier reef enclosing a lagoon between the reef and the land. A barrier reef can encircle an island, and once the island sinks below sea level a roughly circular atoll of growing coral continues to keep up with the sea level, forming a central lagoon. Barrier reefs
Coral Sea whitetip reef shark ("Triaenodon obesus", 21%), silvertip shark ("Carcharhinus albimarginatus", 10%), tiger shark ("Galeocerdo cuvier", <1%) and great hammerhead ("Sphyrna mokarran", <1%). The interaction rate (free diving) at the Coral Sea reefs ranged from a few to 26 sharks per hour. The rare "Etmopterus dislineatus" shark species is endemic to the central part of the Coral Sea. It has been observed at depths of 590–700 m on or near the continental slope. The coastal areas of the Coral Sea were populated at least 40,000 years ago by prehistoric people descending through the northern islands. Those Aboriginal tribes have been dispersed