Lizard and Heron Island, Australia
Possibly the largest living structure in the world, the Great Barrier Reef runs about 1,200 miles along the coast of Queensland and ranks at the top of many a diver's bucket list. A national park since 1975, and World Heritage Site since 1981, the reef is about 33 percent fully protected.
Heron Island and Lizard Island both sit directly on the Great Barrier Reef, offering divers easy access from white-sand beaches to coral gardens and pinnacles and the 1,500-plus species of reef fish that live there, along with turtles, manta rays, reef sharks, and a variety of marine invertebrates. The waters around these islands are relatively shallow (average depth between 30 and 80 feet), and the reefs mere feet from shore.