Danish and Swedish swimmers have been warned to keep their swimwear on when they are in the Öresund Sound, which is located just off the southern coast of Sweden, because a relative of the piranha was discovered in the water.
A fisherman pulled in a 21 centimetre pacu recently, which lead experts to warn eager swimmers of the perils that could come with encountering the nautical beast.
The Natural History Museum of Denmark wrote, "Keep your swimwear on if you're bathing in the Sound these days - maybe there are more out there!"
The fish usually lives in warmer climates, and an expert has confirmed that their diet consists of eating the private parts of men.
Henrik Carl, a fish expert at the Danish museum, remarked, "The pacu is not normally dangerous to people but it has quite a serious bite, there have been incidents in other countries, such as Papua New Guinea where some men have had their testicles bitten off."
Carl then explained, "They bite because they're hungry, and testicles sit nicely in their mouth. And its mouth is not so big, so of course it normally eats nuts, fruit, and small fish, but human testicles are just a natural target. It's not normal to get your testicles bitten off, of course, but it can happen, especially now in Sweden."
Fishermen, whose testicles have been bitten off, have even died because of their injuries because of blood loss.
Swedish officials are still unsure if there are any still left in the water though, and a team are now investigating DNA of the fish to confirm if it's a pacu.
The fish is remarkably similar to the piranha, as they are a member of the same family, with Carl adding, "They are almost identical to the piranha, you couldn't even tell from the outside. It's just that they have different teeth. Flatter and stronger, perfect for crushing."