Such days are gone. In just a few decades, the Caribbean’s reefs have collapsed. Golden beds of elkhorns and staghorns have disappeared and been replaced by thick mats of green algae. The proportion of the reef covered by live coral has plummeted from 50% in the 1970s to just 8% now, changing the fish communities dramatically. “Florida was a scary place to snorkel then, with hammerhead sharks, groupers and sailfish,” says Bruno. “Now, it’s like snorkelling in an aquarium.”

It’s not just the Caribbean. A third of reef-building corals are in danger of extinction, and reefs the world over are in serious decline. Even Australia’s Great Barrier Reef, long held as a shining testament to careful management,