Giant lion's mane jellyfish filmed off Pembrokeshire coast

A giant lion's mane jellyfish was filmed off the coast of Pembrokeshire, Wales, near Trefin Beach. The specimen, recorded by 21-year-old free diver and conservationist Iestyn Morgan, was estimated to be between 10 and 15 metres in length, a size Morgan compared to a bus or a small train.

While lion's mane jellyfish are typically found in the colder waters of Scotland, they occasionally appear in Welsh waters during late summer or autumn. Marine biologist Dr. Cathy Lucas from the University of Southampton noted that while the species possesses the most severe sting in UK waters, it is not considered dangerous to humans. She advised that contact should be avoided and that any stings should be treated by removing tentacle fragments with a stick and washing the area with warm water.

Morgan, who records footage to raise awareness about marine threats and changing ocean ecosystems, noted an increase in jellyfish and Mediterranean fish species entering Welsh waters. The lion's mane jellyfish is known for its extremely long tentacles, which can extend between 30 and 36.5 metres, making it one of the longest animals on Earth.