The Great Barrier Reef is one of the great natural wonders of the world, the largest coral reef on Earth. It is a system of many individual reefs and small islands. Altogether there are 2,900 individual reefs. It lies in the Pacific Ocean off the coast of Queensland in northeastern Australia. From north to south its length is more than 2,000 kilometers.
The Great Barrier Reef was formed over millions of years from mounds of coral. There are at least 300 types of hard coral. The corals died but their shells remained, and other corals grew on top of it. Over those millions of years, the corals cemented together and were covered with underwater plants, debris from the ocean. Most of the reefs are under water (bare during low tides).
The sea life of the reef is extraordinary. And there are more than 1,500 species of saltwater fish. Besides the 400 types of coral, there are anemones, sponges, snails, worms, lobsters, prawns, jellyfish, crayfish, giant clams, and dugongs.