12. Arapaima gigas
The Arapaima gigas is a massive Amazonian fish also known as a pirarucu, and this monster can grow to a length of more than 10 feet. The largest specimens can weigh as much as a hefty 400 pounds. In fact, this fish is not going to attack you. But bumping into one while you’re swimming in the Amazon is sure to give you a fearful shock. Sadly, this fish actually has more to fear from us due to overfishing.
Now here is a fish that could give you serious nightmares. Not because it will try to eat you, poison you or electrocute you, but purely because of a remarkably strange facet of its appearance. Open its mouth and take a look inside. The pacu appears to have somehow got hold of a set of unmistakably human teeth. Although actually related to the piranha, the pacu, which can weigh well over 80 pounds, sticks mostly to a vegetarian diet.