It sounds like something out of a 1950s B-movie, but Brits are worried about an invasion of gigantic jellyfish after a second one was spotted this week.

Estimated to be 8 feet long, the second giant barrel jellyfish was discovered by a member of the Fowey Shellfish Company while checking equipment on Tuesday, SWNS reports. The owner of Fowey Shellfish, Will Hancock, was surprised by what he saw.

"I get in the water sometimes to look at our site and out the corner of my eye I saw something that was bigger than me," the 35-year-old Hancock said in comments obtained by SWNS. "It was at least 8 feet long and probably 4 feet wide. It was the biggest one I've ever seen."

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The first jellyfish was spotted on Monday in Falmouth, Cornwall, by a pair of divers who were swimming next to it.

It's unclear exactly why the jellyfish are swimming so close to shore, but experts believe the warmer weather may be a factor, causing their prey to move their locations. There's also concern that there may be more of them, particularly at a time when tourists and vacationers are spending more time near the coast during the summer months.

We'll see a lot more of them, absolutely. I wouldn't even say we've seen the biggest yet, they'll keep coming in August and September because they like the warmer weather. — Will Hancock, owner of Fowey Shellfish

Dr. Victoria Hobson, a marine ecologist who specializes in barrel jellyfish, said that we're seeing more of them now because the waters off the British coast are "clear and flat."

"There are lots of sunfish around at the minute and they eat them, the sunfish like the warmer weather," Dr. Hobson noted.

The large jellyfish, which can sometimes wash up on shore in the "hundreds," according to Wildlife Trusts, are attracted by plankton blooms. They do have natural predators however, as they are considered "the favorite food of leatherback turtles, the world's largest sea turtle."

"It's probably because of what they feed on, that's why they're getting so big," Hancock added. "They've got so much to feed on that [they are] growing quite large. They're becoming more abundant, people are catching them in their trawlers. We'll see a lot more of them, absolutely. I wouldn't even say we've seen the biggest yet, they'll keep coming in August and September because they like the warmer weather."

Dave Swiggs, a director of Fowey Shellfish, said that the jellyfish was "probably six or seven feet," adding that Hancock told him he was careful not to get too close to it.

"It was massive, he was careful about getting too close to it - he's not a fan of jellyfish at the best of times," Swiggs added.

Though they are not deadly or poisonous, Hancock and others have a right to be fearful of the barrel jellyfish, as they can still sting even after they've died, Wildlife Trusts noted on its website.

"They do have a sting but it's quite mild, it's like a nettle sting," Hobson continued. "I would highly recommend you don't go hugging them though."

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Fox News' Madeline Farber contributed to this story.