Reef
A reef is a rock, sandbar, or other feature below the water surface (less than 80 meters below low water).
The best-known reefs are the coral reefs in tropical waters. They are built by corals and calcareous algae. Artificial reefs such as shipwrecks are sometimes created to attract fish and other organisms.
Reefs in the Louisiade Archipelago
Reef Media
Coral reef at Nusa Lembongan, Bali, Indonesia
Pamalican island with surrounding reef, Sulu Sea, Philippines
A reef surrounding an islet
Part of Great Barrier Reef
Fossil brain coral (Diploria) at the Windley Key Fossil Reef Geological State Park. US Quarter near top for scale.
