'We are rewriting the textbooks': first dives to Amazon coral reef stun scientists

Scientists have discovered the river reef is far bigger, and more important, than first thought - a biodiversity hotspot on a par with the Great Barrier Reef. Now they face a race to protect it from big oil

There is a flickering, bright glimmer of sky as the two-person submarine descends beneath the muddy equatorial waters to a place no human has ever seen - a vast, complex coral reef at the mouth of the world's greatest river.

Thirty metres under the murky plume of the sediment-heavy Amazon, the sub enters a darker, richer world. A school of curious remora fish approaches the two-tonne machine. Crabs and starfish loom in its eerie lights. A metre-long amberjack swims past, then a two-metre ray.