A shark warning has been issued in Cornwall after one of the animals was spotted swimming unusually close to shore.
The six-foot blue shark was discovered in shallow water in the River Fal on the National Trust's Trelissick estate between Truro and Falmouth on Wednesday.
Blue sharks are one of several species of shark known to migrate from the Atlantic to the west Cornwall coast during the summer months.
However, experts warned that the shark should be "given a wide berth" because the animal could be injured and stressed.
Dan Jarvis, of the charity British Divers Marine Life Rescue, said his team was monitoring its condition over fears the shark could be disorientated.
'Ignore it and give it a wide berth'
Mr Jarvis said: "This is a real worry for us because they don't normally come up so close to beaches like this. Our worry is that it is injured or unwell and might need some medical attention.
"Our advice is to ignore it and give it a wide berth. It could have just come for a look and will swim off when it's happy to, but if it's unwell we don't want to cause it any more stress by people getting into the water and interfering with it."
Dog walker Harry Gooby, who filmed the shark, said it appeared the creature was trying to make its way onto the shore.
Mr Gooby said: "I was waiting less than a minute when a shark swam very close to the shore and at one point put his snout up onto the beach.
"His whole head came out of the water and almost nuzzled the underneath of its neck on the beach."
Some swimmers raised the alarm over the creature's presence.
Volunteer medics have pledged to come to the aid of the shark if it is stranded on the sand and will be keeping a close eye on its health.
It comes after a woman snorkeler was bitten off the coast of Cornwall earlier this month, the first shark attack in Britain in 175 years.
The diving trip had been organised by the Blue Shark Snorkel tour company to give people a close-up view of blue sharks.
But at some point during the dive one of the predators - thought to have been a blue - is understood to have turned and bitten the woman.
The largest blue shark ever uncovered in British seas weighed 256lbs and measured over 9ft.