Visible from outer space, the Great Barrier Reef runs the entire length of Queensland. Created by living coral over the span of 18 million years, the reef is 2,000 km (1,243 mi) long, and in places more than 500 m (1,640 ft) thick. Particular about its living conditions, Queensland's coastal waters prove ideal for sustaining both living coral and the hard skeleton left when it dies. Approximately 2,600 smaller reefs and 400 types of coral comprise the Great Barrier, some of which are poisonous, and thousands of species of fish, sponge, crustaceans and molluscs find their habitats here. A natural wonder of the world, it is punishable by law to touch or remove any piece of the reef.

Northern Queensland's coast is mere 50 km (30 mi) from the reef, and cities like Cairns, Townsville, Port Douglas and Mackay offer several tours and excursions to areas suitable for snorkeling and diving. Live aboards, or floating guest accommodations make it possible to spend several days studying the reef, its delicate balance protected by the Great Barrier Reef Marine Park Authority.