Fish name: Piraiba Catfish US Location: None Worldwide Location: Amazon, South America Why is it dangerous? This fish is the largest catfish in South America, and it's got a reputation to go with that name. The fine teeth of this aggressive hunter curve backwards across a cavernous mouth, preventing prey – including humans – from escaping its grip. Still, they haven't been proven to have eaten any humans. Should I be worried? If you're fishing in the Amazon, you could accidentally catch one of these monsters. It's huge teeth are dangerous, and you should be aware of their presence when in the rivers of the area.