There are reefs and there is THE REEF. Australia's Great Barrier Reef remains at the top of many a diver's bucket list, and with good reason. Named as one of the seven wonders of the natural world, it is the largest coral community on the planet and one of ocean's most biologically diverse habitats. It's all here, from the tiny and the exotic to the largest fish in the sea. Explorations can begin at land-based resorts in Cairns or on Heron Island, while liveaboards give access to renowned sites on the Ribbon Reefs and the Coral Sea. Ashore, all the natural and cultural discoveries of the Land Down under await.