After the tsunami and other events (tourists, fishing etc) this (see photo) is what you find in many places, even in national marine parks in Thailand. Corals like these grow about one centimeter every year.
Everyone who goes diving or snorkeling in Thailand will see that there is an enormous difference between the marvellous descriptions of marine life and the real thing. Nothing to do about that; you have to enjoy what you see.
Better concentrate on small things. Like this coral which maybe will grow bigger every year.