The pacu, a cousin of piranhas, has a bad reputation. Although it has round, dull teeth, the fish "has reportedly earned a bad reputation after castrating a couple of local fishermen" in Papua New Guinea; it "occasionally mistakes testicles for tree nuts." And a ten-incher was caught by a 77-year-old retired bus driver in New Jersey over the weekend. "Most likely, someone had it in their fish tank and it grew too big, so they dumped it," said a fish-store expert. "We call them 'tank busters.' We don’t even sell them because they grow so big." We'd call it something far worse.
You've been warned, skinny-dippers of New Jersey's natural waters.