BBC Earth producers have had an exhilarating encounter with seven sharks measuring up to six metres long.
The crew were filming what happened to a sperm whale carcass from about 750 metres deep in the Atlantic Ocean, near the Azores off Portugal, for the documentary Blue Planet II.
But the bluntnose sixgill sharks feeding off the carcass made for even better television when they initially began fighting each other – and then went for the submarine.
“He’s pushing us,” one crew member said as the sharks knocked them about.
“The submarine is so strong, but they’re so big and strong that I’m a little bit afraid,” another said.
Will Ridgeon, a producer on the expedition, told The Sun the gore of the flesh and blood was “like a horror movie”.
“They became aggressive and mistook us as a competitor for the carcass. They began smashing up against us and biting the sub,” he told the newspaper.
“Once we got over that initial fear it was one my best moments of the series.”
The bluntnose sixgill sharks were most likely merely investigating the submarine after being startled by its lights, and probably weren’t attacking.
Former ReefQuest Centre for Shark Research director R. Aidan Martin said in a blogpost that the sharks were light-sensitive.
“In the deep-sea, ambient light levels are very dim to nonexistent. As an adaptation to this darkness, the pupils of the bluntnose sixgill are permanently dilated – the muscles that formerly contracted the irises have atrophied from eons of disuse.”
The BBC Earth footage offered a rare insight into the feeding habits of bluntnose sixgill sharks, which tore off large chunks of flesh from the carcass.
Mr Martin said little was known about the creatures due to their “inaccessible habitat”.
“They typically haunt depths of 300 feet (90 metres) to at least 6150 feet (1875 metres) – far too deep for observation using conventional scuba gear, and much too expensive to study using deep-sea submersibles.
“Sporadically, a bluntnose sixgill turns up in relatively shallow water, but usually at night and never predictably.”
He said most information about the bluntnose sixgill sharks, which are found in oceans all across the world, came from examining their carcasses.