The Pirarucu is one of the largest freshwater fish in the world and can be found mainly in South America. It can grow up to a maximum length of 4.5 meters and weigh up to 220kg! Unfortunately for them, they are also pretty good for food and are thus caught frequently to be sold in the markets. Another unique thing about this fish is its ability to breathe air from the surface as it has lung-like linings in its throat. It can therefore survive extensive drought periods by gulping air and burrowing in the mud or sand of swamps. Talk about ‘Natural Selection’. In addition, the tongue of this giant is believed to possess medicinal qualities and is taken to kill intestinal worms. Though they are harmless to humans, I would be pretty freaked out if one came swimming near me!