Great Barrier Reef, the world’s largest barrier reef, is a system of coral reefs and islands that stretch 2,010 km (about 1,250 mi) along Australia’s eastern shore. An almost continuous line of breakers marks the location of the outer reefs, which line the rim of the continental shelf. Between the outer reefs and the beach are many crescent- or horseshoe-shaped inner reefs.
The clear, warm, shallow waters of the Coral Sea provide ideal conditions for the corals and algae that make up the reef, and for the extraordinarily diverse marine life related to the reef system. The small islands that top some of the inner reefs are stabilized by vegetation growth. Many have been made national parks, and some of the reefs are marine national parks.