The polyps secrete the hard outer shells that give the reef its structure, with generations up reefs building upon themselves over thousands of years.
Most corals prefer to grow in clear, warm tropical waters.
This particular section of the Great Barrier Reef was rich in large clams. These large black clams were approximately four feet across and could be found both in the coral and on the nearby sand. They filter water through the large siphon barely visible in the center. Smaller, but more vibrant, were the bright blue clams. In between, in terms of both size and color luminosity, were the clams with irridescent green spots.