Crossbreeding corals: the hunt for ways to heal the Great Barrier Reef

Scientists, farmers and volunteers are looking for ways to lessen the impact of climate change as experts warn a third mass bleaching has taken place

• Photographs by Jonas Gratzer

One of the dive instructors points out two blacktip reef sharks circling a docile green turtle busy grazing on algae. Stingrays of various sizes, colours and shapes pass beneath us. Suddenly, a pod of dolphins appears, swimming over the hard corals.

The dive takes place on what appears to be healthy and pristine coral reef surrounding Lady Elliot Island, at the very southern end of Australia's Great Barrier Reef off Queensland.