That can't taste good. Men in Scandinavia have been told to keep their swim trunks on because the pacu, a fish native to South America, is swimming around biting testicles. But apparently the "ball cutter" or "nutcracker fish" isn't as mean as it looks. Though its teeth are large and frightening, they aren't as sharp as those of their cousin piranha—though still certainly sharp enough to rip through skin. The problem is that the pacu, a vegetarian fish, has been mistaking testicles for its favorite treat, nuts. Could be worse, right? OK, maybe not.