Capricorn and Bunker groups, island clusters at the southern extremity of the Great Barrier Reef off the eastern coast of Queensland, Australia, on the Tropic of Capricorn between Capricorn Channel and Keppel Bay. They are true coral cays, comprising sandy detritus on coral platforms with typical screw-pine vegetation. Sparsely populated, the main islands (Heron, One Tree, Wreck, and North West) are used primarily as tourist resorts and for prawn fishing.