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 . Steve Hussey can grow up to six feet and weigh 55lb .