The two coral cays of Lady Musgrave and Lady Elliot Islands are the closest pieces of the Great Barrier Reef to Bundaberg and the cheapest way to see it from mainland Queensland.
Lady Musgrave Island is a 14-hectare cay inside a 1,200-hectare lagoon, reached by daily high-speed catamaran (about 2 hours each way) from Bundaberg Port Marina. Day trips include snorkelling on the lagoon, a glass-bottom boat tour, and a couple of hours on the island itself.
Lady Elliot Island has an airstrip and is reached by 30-minute light aircraft from Bundaberg airport. Day trips and overnight stays at the eco-resort are available. The island sits in deeper water — manta rays are nearly guaranteed in winter, and the wall snorkelling is the best easily accessible reef from mainland Australia.
Either is a long, expensive day; both are worth it. Book well ahead.