A shark isn't really something you really want to spot while you're on holiday or even in your home town - which is pretty daft considering they're just mooching around their own habitat.
And following the latest encounter, the public have been warned to stay out of the water in St Ives, Cornwall, after a massive shark was spotted swimming in a harbour.
The nine foot beast was filmed close to the shore at the popular Cornish holiday hotspot. It's thought to be either injured or lost its bearings chasing prey.
Footage of the predator was captured by workmates Archie Pickin and Harry Hocking, both 16, who were standing on the harbour slipway.
The pair were about to start work on the hire boats Monday morning at about 9.30am when they first noticed it.
Archie said: "We heard someone say about a shark and we didn't believe it at first. It doesn't exactly happen every day. It was really big."
Harry added: "It was swimming along for a good two to three minutes and went towards west pier before leaving the harbour.
"A lot of people noticed and by the time it left there were dozens of people watching from the harbour wall.
"People have already been saying they won't be swimming now."
Experts believe from footage shows a blue shark and have warned the public to keep its distance while it remains in the area.
John Richardson of the Shark Trust said: "They are predominantly an oceanic, open water species, and not commonly found close to shore.
''But it is certainly not unprecedented to see one in such shallow waters. To see a free-swimming blue shark close to shore like this is a real privilege.
"If this shark remains in St Ives harbour, the Shark Trust advises people to give it plenty of space until it moves back offshore to its usual habitat.
"Due to the confined nature of the harbour, which could hinder the shark's ability to naturally move away from disturbance, the trust strongly advises people not to get into the water with the shark.
"We can only speculate on why this shark has come so close to shore. Possible explanations include injury or illness, or perhaps disorientation after following prey inshore. But this is speculation only."
Blue sharks are the most heavily fished shark in the world. In European waters the species is listed as Near Threatened on the IUCN Red List of Threatened Species.
Featured Image Credit: SWNS