A Mola mola fish - nicknamed the ocean sunfish - was spotted by diver Ian Hope-Inglis, 52, who saw the creature bobbing around a reef in Devon.
The flat-fish, which is as tall as it is long, has a peculiar flattened body and is the heaviest of all bony fishes.
Gobsmacked Ian, who has been diving for eight years, couldn’t believe his discovery on Devon’s Plymouth Sound.
He said: “We were diving not far from the harbour entrance at the Mewstone when my diving buddy gestured for me to come and see something – I thought it would be a lobster.
“I turned around and the fish was there; I have rarely seen the fish in a book let alone in real life.