Many thanks to Robert Lenfert for this excellent footage - This video shows a diver off the British coast swimming next to one of the biggest barrel jellyfish filmed in UK waters. Diver Robert Lenfert spent several minutes in the sea off Pendennis Point, Cornwall next to the large rhizostoma pulmo (corr) commonly known as the barrel or dustbin-lid jellyfish. The creature is harmless to humans but their size gives them an imposing presence. Hundreds of the giant animals have been spotted in Britain's seas over the last few weeks - and although they have a sting it is only very minor.