Ningaloo is Australia's largest fringing reef, 260 kilometres of coral off the northwest coast of Western Australia, and it starts a few strokes from the sand. The continental shelf is unusually narrow here, so the coral built straight onto the old shoreline instead of miles out to sea. That same narrowness brings deep, cool, nutrient-rich water in close, which feeds the reef from below and brings everything else in with it. Turquoise Bay is snorkelled as a drift, with no boat involved. You walk in at the sandy southern end and a gentle current carries you north over branching and brain corals, past parrotfish, angelfish and wrasse, with green turtles crossing between feeding patches. You swim back in before the tip of the sandbar, where the current runs out through a channel. Behind the lagoon the rust-red gorges and limestone ridges of Cape Range come straight up off the coast, so three colours line up: desert red, white sand, turquoise water, with the reef a pale line just offshore.
Seven to ten days after the March full moon the corals spawn all at once. The plankton bloom that follows pulls in 300 to 500 whale sharks, the largest fish alive. A spotter plane finds one from the air and puts the boat in its path. You slide into open water as it comes. Swimmers keep a set distance, so the fish sets the pace, and mostly it just glides on while you work to keep up. The manta rays never leave. You get in ahead of a feeding one and hold still: it comes on with its mouth wide open, somersaulting through the plankton, and a wing three or four metres across passes an arm's length beneath you. From November to March green, loggerhead and hawksbill turtles haul up these beaches after dark to lay. The pale spots behind a whale shark's gills are unique to the animal, so they are known from photographs rather than tags, and the same ones come back to this piece of coast year after year.