They have been washing up on beaches across the south west for weeks, and now the giant barrel jellyfish are enjoying a swim off Falmouth.

This beast was photographed by Sean White off Gylly Beach while paddleboarding.

Liam Brennan of Gylly Adventures, who was one of the paddleboarders in the group, said: “We paddled the other day towards Maenporth and saw about 4 or 5. They’re in this bay too.”

“I’ve seen a lot of them, they’ve been around for the last couple of weeks.”

This one was spotted as it swam under a Nankersey club's gig boat this week

Falmouth Packet:

According to the Marine Conservation Society you are most likely to see barrel jellyfish from a boat while out at sea as they are less common close to the coast.

Known as the 'basking shark' of jellyfish due to its large size, they feed on tiny plankton, but the creature's sting is not powerful enough to harm humans.

Jellyfish are the staple diet of the critically endangered leatherback turtle. These spectacular reptiles are seasonal visitors to UK seas, migrating from their tropical nesting beaches, and analyses of stomach contents of dead leatherbacks stranded on UK shores have revealed that they feed on several species of British jellyfish.

The MCS say, Barrel jellyfish are unmistakeable, their large bodies highly visible, and the smooth bell and cauliflower-shaped mass beneath very distinctive. Jellyfish are classified as Scyphozoa, from the Greek scyphos, a cup, and zoon, an animal. The specific name 'octopus' means 'with eight legs' (or arms), and has nothing to do with octopus - except, of course, that they are named 'octopus' for the same reason.

The scientific name Rhizostoma means 'root pores', and gives a clue as to how the barrel jellyfish lives. The big 'arms' of this impressive jellyfish trail behind the huge, solid bell, and are quite complex structures. They are fused together for much of their length, and on the highly convoluted 'cauliflower' part, beneath the bell, are hundreds of tiny mouths (the 'pores'), leading to a highly branched digestive system.

Each mouth is surrounded by tiny stinging tentacles, able to catch plankton small enough to enter the minute mouths. Rhizostoma is the 'basking shark' of jellyfish - despite its huge size, it lives on tiny plankton, and its sting is not powerful enough to harm humans.

The barrel jellyfish often has tiny passengers in the form of stout amphipods (Hyperia galba), crustaceans up to a centimetre long, that hang onto the jelly with spine-like feet, often inside the stomach or reproductive cavities. These crustaceans can change colour to match their background, blanching while among the jellyfish tissues to avoid detection - small fish, which might eat them, often accompany this jellyfish.