Why they're dangerous: Wade accidentally encountered one of these testy beasts while looking for goonch catfish in India. "It actually made a lunge for one of the local guys who was with me," he says. "It happened so fast, I couldn't see it. Only when we played the film back did we see its 18-inch neck shoot out very close to this guy. The jaws are like bolt cutters. I was hanging onto it, and it was almost pulling me into the river. It was like a tank. I would really not want to be bitten by those."

How to stay safe: These bottom feeders don't often come into contact with people, so you're unlikely to face off against one. But Wade advises that if you're swimming in India, "don't make sudden movements if you feel something in the water."