If there's still a place for giants on this planet, it's in the depths of the seemingly endless ocean.

Even there, humans occasionally bump into a behemoth.

Like this barrel jellyfish.

A barrel jellyfish swimming in the ocean with a diver Despite packing stingers on each of its eight tentacles, the jellyfish didn't seem to mind the company. (Photo: Dan Abbott)

Underwater cinematographer Dan Abbott and biologist Lizzie Daly were diving just off the coast of Cornwall this week when this tentacled titan emerged from the murky waters.

Rumors of box jellyfish growing as big as — and bigger — than humans had long been known to science. But to suddenly find yourself alongside one is a different story as they're rarely seen, aside from when a corpse occasionally washes up on a beach.

"It's known to get this large, but I haven't seen one this big." Daly, who is also a wildlife presenter for the BBC, tells CBS News. "Dan said he hasn't seen one this big either."

And what do you do when you're surprised by a creature of downright mythological proportions?

Well, when you're as passionate about ocean life as Daly and Abbott — the pair were on a seven-day expedition to raise awareness about marine life — you bask in its glory. And, of course, keep your finger on the video record button.

"It really humbles you to be alongside an animal that size," Daly tells Motherboard. "It's an experience we'll never forget."

Daly ended up swimming with the jellyfish for about an hour, while the video Abbott captured would become a massive viral sensation.

For the jellyfish's part, it didn't seem all that bothered by the gawking humans in its entourage. Not bothered enough, at least, to flash its stinger.

In fact, this jellyfish has eight arms, each with stinging tentacles.

The thing is, for all its daunting dimensions, the barrel jellyfish doesn't pack much of a wallop. At least, not the potentially deadly attack a box jellyfish is known to unleash.

"They're not a threat to humans," Daly explains to CBS. "They have a mild sting, but wouldn't cause damage to humans."

But, as we see here, this creature is capable of stunning us all with just one glorious look.

Watch the full, mesmerizing video below:

Astonished divers come across a massive jellyfish off the coast of England
Divers enjoy a swim alongside a human-sized jellyfish near Cornwall, England.