This huge barrel jellyfish was spotted by the team at 7th Rise beside the River Fal while out for a paddle.
Thom Hunt, the owner and resident at 7th Rise, who is also a marine biology graduate, said he has never seen one this large before.
People finding the jellyfish, which are not harmful to humans, are being asked to report their sightings to conservation groups such as the Marine Conservation Society
7th Rise provides unique adventure courses and experiences beside the River Fal in Cornwall, and teach traditional techniques from foraging, fishing and bush craft through to wild food butchery. More at www.7thrise.co.uk.