There has been an unusual warning for male skinny-dippers in Scandinavia.
Experts say they should watch out for this fish, infamous for biting testicles.
A fisherman discovered it recently in the Danish-Swedish strait of Oresund.
It's called a pacu and its native to South America.
Experts with the Natural History Museum of Denmark say its unclear how the fish wound up in the strait.
Pacu fish are generally known as vegetarian cousins of the piranha.
They are known for crushing nuts with their powerful jaws and experts say they can sometimes mistake the male reproductive organs for their favorite snack.