This week’s warm weather may have tempted you to take a dip in the UK’s usually chilly waters. And if you had, you wouldn’t have been the only one swimming around the coastline. Billions of jellyfish have appeared in our waters, apparently attracted by the higher sea temperatures. Scroll down for video . Making waves: Billions of barrel jellyfish have been spotted in water off the coast of Devon and Cornwall . Hundreds of the barrel jellyfish – each the size of a dustbin lid – have been hauled in by fishermen on the Devon and Cornish coast, with dozens of sightings reported to the authorities. Passengers aboard a sea life cruise were stunned after coming across a giant swarm of thousands of the jellyfish – the largest species found in south-west England – over a mile in length on Wednesday. The jellyfish, which can grow up to six feet and weigh 55lb, were sighted just off Pendennis Point near Falmouth, Cornwall. Keith Leeves, captain of AK Wildlife Cruises, said: ‘It was eerie and a little unnerving. ‘There were thousands of them. I’ve never seen anything like that in all the years I’ve been doing this – it was spectacular.’ Invasion: Experts believe the barrel jellyfish, which can grow up to six feet, have been attracted by the warmer waters and a lack of predators . Experts say their stings are not powerful enough to do any serious harm, but warn swimmers that it is best not to touch them. Matt Slater of the Cornwall Wildlife Trust said it was ‘difficult to say what is causing their appearance, but it could be because there is more plankton for the jellyfish to feed on because of warmer waters’. Steve Hussey, from the Devon Wildlife Trust, says the increase could be because of fewer predators in the region’s seas. ‘The leatherback turtle is struggling at the moment, which means there are less of them to eat the jellyfish.’
Creatures attracted by the higher sea temperatures .
Dozens of sightings reported by fisherman off Devon and Cornwall .
Jellyfish can grow up to six feet and weigh 55lb .