If you or any of your friends go fishing, you’ll no doubt be aware of some of the big fish that it’s possible to land. But unless you live deep in the South American rainforest, it’s unlikely that you’re ever going to come across a fish as enormous as the arapaima. These freshwater monsters are some of the biggest fish in the world and can come in at an amazing 4.5 meters!

They weigh hundreds and hundreds of pounds. They’re freakishly big. But the most unusual thing about these giant fish? They breath through their mouths! They come up to the surface for air. Leaving them easy to hunt and fish. So they’re becoming an endangered species.

Also known as the ‘pirarucu’, the primitive lungs make them unique in the freshwater fish world. They also have gills, so can breathe under water. But they generally live in oxygen-poor water, so they have adapted the lung to survive.

Watch what happens when a documentary crew get up close and personal with a large arapaima…