The biggest of the turtles can grow up to a couple of metres in length
A rare giant leatherback turtle has been spotted off a beach in Lancashire.
The turtle, which is a critically endangered species, was seen by Simon Smith as he was out walking his dog on the beach at Cleveleys on Monday.
Mr Smith said he saw it about 50 yards (46m) offshore and watched for about two hours as it fed on jellyfish.
The Marine Conservation Society (MCS) has urged coastal path walkers and people in boats to look out for the turtles and report any sightings.
Mr Smith said: "The sea was very calm, and I was throwing the ball in for the dog to fetch when I noticed this big thing floating about 50 yards offshore.
Leatherback turtles face threats to their survival including habitat destruction and the disturbance of their tropical nesting beaches
They can get entangled and drown in fishing gear and die from starvation when they eat plastic litter, which they mistake for jellyfish
The biggest of the turtles can grow up to a couple of metres in length and weigh up to a tonne - about the same as a small car
MCS said four other sightings had been reported this year, including two off west Wales, one off the Isle of Man and one off the Isle of Skye at the end of May
"It looked like a corpse in a body bag."
He added: "I threw the ball closer and it dived and then resurfaced further down the beach.
"I followed it and watched it with binoculars and realised it was a giant turtle.
"It was probably about six feet long. At first we thought it might have been a seal injured because it was moving quite slowly.
"I got within about 30 yards of it at one point and watched it for about an hour and a half before the light faded.
"It wasn't scared at all, and because there were a lot of jellyfish about I think it must have been feeding. It was a truly amazing experience."
Peter Richardson, Biodiversity Programme Manager from the Marine Conservation Society said the turtles have been seen in Lancashire before: "They do come to UK waters every year, and they have been spotted close to Blackpool before, but it's very rare that someone actually gets to see them.
"They nest in the tropics, but they are specially adapted to life in cold water; they can actually maintain their body temperature at about 18 degrees above that of the sea, so they're unique among reptiles as they're pretty much warm bloodied.
"That means they can come to our chilly seas and time their arrival in UK waters just as our jellyfish are starting to bloom, and that's what they're coming for."
Mr Richardson continued "Simon did absolutely the right thing, he watched that turtle, he took notes of what it was doing and then he reported it to the Marine Conservation Society.
"Keep your eyes peeled and if you see a leatherback, enjoy the experience because you're very lucky if you do see one."