The two divers, James Parkinson and Andreas Klocker, were asked by the Institute for Marine and Antarctic Studies to explore the 200-metre-long deep granite reef in the Freycinet Commonwealth Marine Reserve.

The divers found a rainbow of sponges and corals, including tree-forming black corals that may be new to science.

“It’s the best, most exciting ocean-diving experience we’ve ever had by a long way,” Mr Klocker said.

“The lower light levels take you below the greenish realm of kelp forests and into an incredible riot of colour.”