Great Barrier Reef islands off the coast of north Queensland comprise coral islands, vegetated sand islands and continental islands.
The true coral islands are called cays and have been formed by dead coral ground down to sand by the action of the sea. They are low-lying islands which may or may not have vegetation.
Some large cays have been developed as tour destinations and even as island resorts such as Heron Island off Gladstone.
South of the Great Barrier Reef are vegetated sand islands, such as Fraser Island (Australia’s fourth largest island) north of the Sunshine Coast or North Stradbroke off the Gold Coast.
Closer to shore along the Queensland coast are continental islands which in ages past could have been land peaks which eventually became encircled by water. These include Great Keppel, the Whitsundays, Hinchinbrook and Dunk.
These continental islands may have fringing reefs as well but, strictly speaking, are not part of the Great Barrier Reef.