All coral reefs began life as a single polyp - a tiny, sea anemone-like soft marine animal - which attached to a hard surface. Stony coral species live as colonies and exude calcium carbonate, which forms an external skeleton. As the polyps grow and die, these stony corals create vast reefs.

There are 3 basic kinds of coral reefs: fringing reefs, barrier reefs, and atolls. Fringing reefs grow in shallow waters close to the coast. Barrier reefs are separated from land by a lagoon, growing parallel to the coast and forming a large and continuous reef. Atolls are ring-shaped reefs that develop near the sea surface on underwater islands or islands that sink, or subside.

Like their jelly fish and sea anemone relatives, coral polyps have stinging tentacles that they use to catch food. During the day, these tentacles are usually tucked away, out of reach of hungry fish and other marine animals. But at night they unfold to catch their prey, mainly plankton - small plants and animals floating in the currents.

The Jewel in the Crown
In the Indo-Pacific region is the coral triangle, a magical underwater tapestry created by the collision of tropical light, warm sea temperatures and oceanic currents. It is home to 75% of all known coral species.

Despite surviving for thousands of years, the impact of man's activity seriously threatens the future viability of many coral reefs. The main identified problems are:
Destructive fishing practices
Overfishing
Pollution
Sedimentation
Coral mining
Careless tourism
Climate change

One of the major threats to the health of corals around the world is climate change.

Other significant problems include loss of natural habitat and increases in human activity which disturb the natural structure of the corals.