Credit: Animal Planet

Why they're dangerous: These sharp-toothed South American creatures have a fearsome reputation, but Wade says they're actually not as fearsome as certain horror movies would have you believe. The image of a pack of piranhas skeletizing some hapless swimmer just isn't realistic. "If you look at the teeth, they certainly have the potential to be very dangerous," says Wade. "But most of the time they're not exercising that potential." There are situations where piranhas can be dangerous, however, such as when environmental or ecological changes interfere with their normal feeding. "I did talk to a family a couple of years ago, some people living on a floating house, and a 2-year-old toddler fell into the water," says Wade of one grisly piranha incident. "They just couldn't rescue the child."

How to stay safe: Keep out of the water when peckish piranhas are likely to be about. "The golden rule in most situations is: Talk to the local people," says Wade. "They'll know. If they're in the water, it's normally safe."