WHAT'S UP WITH THAT? The Great Barrier Reef is the largest structure ever built by living creatures. Some coral reefs glow in ultraviolet light. For reproduction corals send forth over a billion spawn into the sea. Over 400 different types of coral grow on the Great Barrier Reef. Scientists think that the Great Barrier Reef started forming over 30 million years ago. The foundations of the Great Barrier Reef lie about 492 ft. below the water's surface, which is over three times the maximum depth at which reef building corals grow. Scientists think that the reef started out as a fringe reef which sank when movement of the Earth's crust lowered the level of the ocean floor. WHAT'S UP WITH THAT?   HOME