Why pick one gigantic, ugly fish when you can pick three? First up is the rarely seen oarfish, an eel that is the Guinness Book of World Records holder as the longest bony fish in the world. Oarfish really a family of several species can grow to as long as 56 ft. in length. While they usually live in deep water, they can sometimes float to the surface when dying a habit that's caused them to be mistaken for mythical sea serpents. The Brazilian arapaima is the biggest freshwater fish on the planet they can reach 14 ft. and tip the scales at more than 400 lbs. Unfortunately for their survival, arapaima are also very tasty the species is threatened by overfishing. That's not something the very nasty giant snakehead has to worry about, though. The Southeast Asian river fish is pretty big, but it's also extremely aggressive, attacking anything that might threaten its young including human beings. The snakehead can walk on land with its soft pectoral fins, and even breathe air for a little while. Don't make one mad it will find you.