The swimmer, who suffered a leg injury on Thursday, July 28, was rescued by HM coastguard in Penzance, Cornwall. The casualty was then left in the care of paramedics.
HM Coastguard confirmed that it is believed the injury was caused by a suspected shark bite, reports Cornwall Live.
A spokesperson said: “HM Coastguard sent Penzance Coastguard Rescue Team to meet a snorkeler who suffered a suspected shark bite.
“The coastguard was notified just before 12.30pm on Thursday (July 28). It is believed the swimmer suffered a leg injury.
“The coastguard team met the casualty at Penzance harbour to assist with passing them into the care of the ambulance service.”
Shark attacks remain rare, especially in the United Kingdom.
Several species visit the Cornish waters every year, including blue sharks, porbeagle sharks and basking sharks. None of them tend to attack humans.
The British Sea Fishing website reports: “Blue shark attacks on humans are extremely rare but have been recorded.
“In total, on a worldwide basis, there are four confirmed cases of fatal blue shark attacks on humans with twenty-five confirmed non-fatal attacks.
“In August 2012 a beach in Ceredigion, Wales was closed to bathers due to the presence of a blue shark.
“The shark was spotted swimming in between boats and came very close to the shore, swimming past tourists in just a few feet of water.
“Later in the same month, another beach in West Dorset had to be closed for an hour and a half due to another blue shark.”
It comes as the compass jellyfish – or Chrysaora Hysoscella to give it its scientific name – have been washing up on beaches across the UK.
While their striking orange and brown markings may look beautiful, they can give a nasty sting so it is best to admire them from a distance.