Two of the gigantic fish, which can grow to around 11ft (3.5m), were sighted in the waters off Polzeath and St Agnes, in Cornwall.A fully grown sunfish weighs up to 2,200 lbs (1,000kg) according to the British Marine Life Study Society, and was last spotted off Britain last December, when a dead one washed up on a Norfolk beach.The glimpse of the sunfish, by Richard Morton of Cardigan Bay Marine Centre, was one of many marine wildlife sightings across the country last week, as the Wildlife Trusts encouraged the public to record what they spotted for National Marine Week.Members of the public joined event leaders nationwide to find a huge array of aquatic creatures, from a European common squid inshore at Porlock Weir, Somerset, to a 330ft-long bed of sand mason worms in Kingsdown, Kent.At Cardigan Bay in Ceredigion, Wales, more than 1,000 sightings of bottlenose dolphins were recorded, along with harbour porpoises and Atlantic grey seals. Common dolphins were glimpsed in various parts of Cornwall, while a volunteer-led rockpooling survey on Skomer Island, Pembrokeshire, uncovered five-bearded rockling and a pike fish.Joan Edwards, the Wildlife Trusts' head of living seas, said of National Marine Week: "It is wonderful to hear of the spectacular sightings people are witnessing, everything from sunstars to super pods of dolphins. We hope these encounters inspire and encourage everyone to get out and about and discover how surprisingly rich our seas are."Marine birds were also spotted as part of the search. Some of the most dramatic sightings were recorded on and around the Isles of Scilly. On 30 July a boat trip saw 17 Cory's shearwaters and 10 great shearwaters – the first this year – and in the last week of July there were more than 750 Manx shearwater sightings around the islands.Sunfish: The facts* Their diet consists mainly of jellyfish.* They are seen as a delicacy in Japan, Taiwan and the Korean peninsula.* They can weigh up to 2,200lbs – the world's heaviest known bony fish.* They can live for up to 10 years.