About half the size of Texas, the world's biggest coral reef is home to creatures ranging from tiny burrowing sea-worms to tiger sharks weighing more than a tonne - as well as dolphins, dugongs, whales, turtles, ponderous potato cod, moray eels and humpheaded Maori wrasse.

See current Diving Specials Stay on the Great Barrier Reef

The reef, proclaimed a marine park by the Australian Government in 1975, provides incomparable vistas of multicoloured coral, sponges and varieties of seaweed.

When scuba diving opened it up in the 1950s, access was difficult, involving a six- to seven-hour journey through often-choppy seas. Today, motorised wave-piercing catamarans whisk visitors to the reef in less than two hours, making day trips enjoyable and easy. Extended trips of up to eight days are available.

For sailors who prefer remaining above water, there is no shortage of choices. Just about every type of sailing and motorised vessel plies these waters. Visitors wanting to dive will find that several companies in Cairns offer scuba courses. Novices can settle for the simple tuition necessary to dive safely, or take a more advanced course leading to divemaster status.

The reef was placed on the World Heritage list in 1981, and is the biggest World Heritage area. It is also planet's largest living thing.