Great Barrier Reef: the scale of bleaching has the most sober scientists worried

Australia's world heritage site is the largest living thing on Earth. But warm water driven by El Nino is bleaching the reef, and a recent report calls for it to be listed as in danger

I pulled on my mask and dropped off the back of the boat into the warm water above Nursery Bommie, a dive site at Agincourt Reef more than 70km offshore from Port Douglas, in far-north Queensland, Australia. It is widely regarded as one of the most spectacular tourist reefs in the area.

As soon as I could start to make out the immense shadow of the bommie (an outcrop of coral reef) looming before me I could see that all around its flanks and on the summit, covered in just a metre of water in some places, were blemishes of white.