Blue Planet II viewers have shared their amazement after learning that sixgill sharks only need to eat once a year.

In an episode that included fish with feet, cannibalistic squid, submerged volcanoes and an underwater lake, it was the footage of a group of sharks enjoying a rare meal of sperm whale carcass that most gripped fans.

Sharks fight over scraps of the carcass.
Sharks fight over scraps of the carcass (Will Ridgeon/BBC/PA)

In Sunday night’s instalment of the BBC One series, narrator Sir David Attenborough told viewers that a few bits of the decaying meat would be able to sustain each sixgill for up to a year.

One fan responded to the revelation on Twitter: “The shark on Blue Planet II who only eats once a year is my #DietGoals #BluePlanet2.”

Another joked: “Poor shark not eaten for a year. You can’t even be around me if I haven’t had a snack in an hour,” while one said: “#blueplanet The shark on the 364:1 diet. That’s tough.”

But despite their minimal eating requirements, behind-the-scenes footage showed how the sharks can get aggressive when it comes to priority seats at the dinner table.

In a clip shared by the broadcaster, the Blue Planet team found their own manned submarine treated as competition and pushed around by the creatures as they closed in on the scene.

As the sharks crashed into the vessel, one crew member said: “He was pushing us to the front … I’m a little bit afraid.”

Another said: “I’ve never seen anything like this. This is unbelievable.”

One of the team, Orla Doherty, told ITV’s Lorraine on Monday that working on the show with Sir David was “everything that you hope it’s going to be – and more”.

She said: “To watch him read the script, that’s the moment when the film finally and truly comes together.”

:: Blue Planet II continues on BBC One at 8pm on Sunday.