"The pacu is not normally dangerous to people but it has quite a serious bite, there have been incidents in other countries where some men have had their testicles bitten off," said Henrik Carl, a fish expert at the Danish museum.
"They bite because they're hungry, and testicles sit nicely in their mouth," he told the paper.
Carl was keen to tell swimmers not to worry too much. "You're more likely to drown than get your nuts bitten off," he said.
The sidebar says: "Related Topics: Nuts and Seeds". Well played, sidebar robot. Well played.