The Giant Jellyfish are harmless. We are seeing a large number of them again this year around the coast of Cornwall
This Barrel Jellyfish (Rhizostoma pullmo) was filmed along with his dog in the Percuil Estuary, near St Mawes by Cornwall Wildlife Trust marine awareness officer Matt Slater. This video was taken last year but they are once again being seen this summer.
They are totally harmless and feed on plankton. They do have stinging cells but they are not able to get through human skin. They can grow to 80cm wide and weigh up to 30 kilos!