The Great Barrier Reef is the world's largest coral reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres over an area of approximately 344,400 square kilometres. The reef is located off the coast of Queensland and was named a UNESCO World Heritage Site in 1981. The Great Barrier Reef is home to more than 1,500 species of fish, 411 types of hard coral, one-third of the world's soft corals, 134 species of sharks and rays, six of the world's seven species of threatened marine turtles, and more than 30 species of marine mammals. It is considered to be one of Australia's most popular attractions. Together with the fishing industry, tourism reels in about $6 billion annually and supports some 69,000 Australian jobs. 

But all of this is at risk.