If you're going swimming in Scandinavia, wear your trunks -- no ifs, ands or nuts.
Authorities are warning skinny dippers about the Pacu, a fish similar to the piranha that really enjoys cracking nuts with its strong jaws. They've also been known to mistake testicles for something nice and crunchy, and they're strong enough to take off a finger.
Fisherman discovered the horrifying little creature, which is native to South America, in the Danish/Swedish strait of Oresund, CNN reports. The Pacu can grow to 55 pounds, has giant teeth and looks angry, but is usually the more friendly cousin of the piranha. That is, until it sees a testicle.
Experts at the Natural History Museum of Denmark, who were notified of the Pacu sighting, warn: "Anyone choosing to bathe in the Oresund these days had best keep their swimsuits well tied."
Locals in Papua New Guinea say they have firsthand knowledge of a fatal testicle bite. Two fisherman are said to have died of blood loss after a Pacu chomped off their testicles, according to Metro. That said, such attacks are uncommon.
Last year, two Pacus were reportedly spotted in Lake Lou Yaeger in Illinois. Officials think amateur exotic fish collectors are the ones releasing their pets into waters where they don't belong. Anyone caught dumping exotic fish can be criminally charged.
It's unclear how the fish got into Scandinavian waters.