Giant jellyfish with '40ft tentacles' captured on camera off coast

A free diver has said he "couldn't believe his luck" after spotting a giant jellyfish off the Welsh coastline.

Iestyn Morgan, from Pembrokeshire, said the lion's mane was the "length of a bus" with a size of about 10 to 15 metres (32ft 8in to 49ft 2in).

The 21-year-old conservationist, who records footage for social media to raise awareness about the "threats our seas are facing", said it was the first lion's mane he had seen in Wales.

More commonly found in the colder waters off Scotland, a marine biologist said although the lion's main sting was "nasty", it was not dangerous.

Morgan said he was swimming near Trefin Beach in Pembrokeshire when he spotted the tentacles in the water.

"Three turned to 10, and then to 20. They just kept on coming," he added.

The jellyfish was so big the tentacles went "beyond the range of visibility".

He initially thought it was a compass jellyfish, which are native to UK waters, before realising it was too big.

"It must have been the length of a bus or small train. I couldn't believe how big it was."

The Wildlife Trusts said the lion's mane jellyfish gets its name from its long tentacles, and have "all the beauty and bite of a lion".

They can grow up to 3m (9ft 8in) in length, but the tentacles - which are used to catch their prey - can exceed 30 to 36.5 metres (98ft 4in to 119ft 8in) making it one of the longest animals on Earth.

Marine biologist Dr Cathy Lucas, from the University of Southampton, said Morgan's video showed the animal's incredible length.

"The tentacles are so long and so fine you might not even see them," she said, recalling how during field work in Scotland divers would get bits of tentacles on them when there were no jellyfish around.

"They still sting after they break off," she said, adding that while the sting was "nasty" and "the worst in the UK", it was not dangerous.

"The advice is not to touch them and if you get a bit of tentacle on your skin flick it off with a stick and wash in warm water to neutralise," she said.

Lucas said lion's manes "occasionally" reach the Welsh coast later in the summer or autumn, according to jellyfish sightings recorded by the public, but their main habitat in the UK was Scotland.

Morgan feels we should be "grateful" they were in Wales, adding they were not "big scary monsters" as some people may think.

"Your biggest problem is if you swim into them. You don't want to get stung by a lion's mane."

Morgan said he was seeing "more and more" jellyfish coming into Welsh waters as he was filming.

He said it was part of a theme in which he was noticing warm water species "becoming more abundant".

"I don't have enough summers to compare it to, but I put down a camera a few weeks ago and saw a Triggerfish, which is native to the Mediterranean," he added.

Morgan said creating his content has been "very rewarding" as he wanted to make aquatic environments "more accessible" to people.

But he was always conscious that he never wanted to harm the animals as part of his project.

"I don't want to turn it into something that I'm going out to hunt the animals or anything," he said.

"I just get in the water, film and swim."