A giant ocean sunfish was spotted off the coast of Cornwall, leaving a local woman confused as to what she saw.

Niki Hicks, from St Agnes, Cornwall, spotted the fish while on a boat trip, seeing something bizarre in the water.

Posting the video on Twitter (@scillyniki), she gained nearly 6,000 views from followers curious to discover what the floating object was.

Known as a jellyfish eater or Mola Mola, the fish is the second largest bony fish on the planet, growing up to 11 ft long and weighing in excess of 1,320kg.

The Wildlife Trust said they can be identified as “a giant grey fish that looks a lot like a swimming head.

“It is huge, flat and circular looking pretty much like a giant swimming head.”

The fish was spotted floating sideways, mistaken by viewers as a dead fish as it flopped along with the waves.

Edward said: “The strangest fish.”

Racheal added: “Ohhh I saw one of those once. Love the nature down there in those islands. I thought it was a dead fish at first…” [sic]

“Bizarre things,” commented another person.

“These can be whoppers and I bet he's stuffing his face with all the jellyfish out there at the mo! My Newquay fisherman mate was always a bit superstitious about landing one…,” wrote someone else.