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Giant 20kg jellyfish filmed off the Cornwall coast

29 June 2014 Last updated at 15:34 BST

A giant barrel jellyfish has been spotted swimming in an estuary near St Mawes in Cornwall.

Cornwall Wildlife Trust's marine awareness officer Matt Slater and his dog swam around the jellyfish to capture this footage.

The jellyfish is said to weigh as much as 20kg and measure around one metre in diameter.