What is “Reef” ? What happens in Australia

A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Reefs may go as deep as 261 feet (80 m) below the surface. Many reefs result from abiotic processes (i.e. deposition of sand, wave erosion planing down rock outcrops, and other natural processes), but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and calcareous algae. Great Barrier Reef The Great Barrier Reef is the