In scenes similar to those seen in the film Jaws, a shoal of sixgill sharks attacked the crew in the submarine.
The BBC team had dived to over 700m to discover what happens to a whale carcass on the seabed, but did not expect to be swarmed by the deadly creatures.
As the submarine waded through the dusty seabed, one crew member could be heard to say: “Dust cloud? Yeah, there’s something going on. Oi, oi, that’s a big shark. There it is.”
Another crew member quickly radioed back to the surface, explaining: “We’re at 750m. We’ve found the whale carcass and enormous sixgill sharks. We estimate they’re about six metres long. Over.
“Oh my god, look at the size of it. They’re huge. I’ve never seen anything like this. This is unbelievable.”
However, while the footage did make the final edit for broadcast, the sharks became more aggressive as they were competing with each other to devour the whale.
In a unexpected turn of events, the sharks seemed to see the submarine as competition and launched an attack against the glass.
One crew member gasped: “They’re biting each other! This is absolutely mad! Gosh.”
As the BBC were forced to censor the crew’s expletives, more sharks began to surround the submarine, as members onboard cried: “Look on the left, ah! Oh he is pushing us! Did you see this? I went backwards and he was pushing us to the front.
“The submarine is very strong, but they’re so big and strong that I’m a little bit afraid. Move, move away! Go! Ah!”
The sharks soon realised that the submarine was not after their meal and they returned to their whale feast.
Blue Planet II continues tonight on BBC One at 8pm.