These scuba divers are among the 2 million tourists who visit the Great Barrier Reef each year. They contribute about $5.6 billion to Australia's economy, according to the Queensland government. Steve Dorsey for NPR hide caption

itoggle caption Steve Dorsey for NPR

A tasseled wobbegong shark (top) lies on the seafloor with the head of a brown-banded bamboo shark in its mouth on the fringing reef of Great Keppel Island on Australia's Great Barrier Reef in August 2011. Reuters/Landov hide caption

itoggle caption Reuters/Landov