Long stretch of coral reef , shoals, and islets in the Pacific Ocean, off the northeastern coast of Queensland , Australia.
The largest deposit of coral in the world, it extends for more than 1,250 mi (2,000 km) along the Australian coast and has an area of some 135,000 sq mi (350,000 sq km). The reef has been formed over millions of years from the skeletons of a mass of living marine organisms. In addition to at least 300 species of hard coral, marine life includes anemones, worms, gastropods, lobsters, crayfishes, prawns, crabs, and a variety of fishes. Encrusting red algae form the purplish red algal rim that is one of the reef's characteristic features.