Loads of people are scared of sharks, but in Britain we don't usually have to worry about them when we go to the seaside.
But people in west Wales got a fright when they spotted a fin above the water at Fishguard.
The 2.5m-long creature swam in close to shore, and one man even managed to take photographs of it.
But don't worry, it's been identified as a Porbeagle shark, which experts say aren't a threat to humans.
They say the endangered species often visit the waters near the west Wales coastline.
But the creatures don't usually come so close to shore, which is why it's unusual to see them.
Ali Hood from the Shark Trust said: "No-one should be concerned.
"They shouldn't stop anyone swimming or canoeing or anything. These sharks have always been there."
Cliff Benson from the Sea Trust, who saw the creature, said he didn't think it was very well.
He said: "After about an hour it began making its way slowly out to deeper water and then presumably back to sea."