There are no river monsters in the Amazon river. There are animals, both big and small, many of which aren’t even close to being as dangerous as people imagine.
But sure, I’ll list some of the most notable creatures that can be found in the Amazon river and its tributaries. They’re not monsters and most of them aren’t even dangerous, but they certainly are amazing creatures:
The arapaima is one of the largest fresh water fish, reaching as much as 3 meters in length. Despite their size, though, they aren’t dangerous at all. They are treated as something of a delicacy, however.
The anaconda is the heaviest snake in the world, though not quite the longest. It can reach over 5 meters in length, with the females being considerably bigger than males. Despite its Hollywood fame, there are very few confirmed attacks on humans, which shouldn’t come as a surprise really they’re big, but not big enough to consider an adult human being a meal. Rather than being horror movie monsters, these are very shy animals that do not show any interest at all in relentlessly pursuing people.
Ah, the infamous piranhas. I bet you can already imagine a swarm tearing a poor horror movie character to pieces. In real life, though, that… really doesn’t happen. First of all, piranhas don’t normally attack people unless exposed to stressful situations; secondly, they do not swarm like in the movies. In fact, piranha attacks usually involve single bites, normally in the hands and feet. Hardly what you’d expect from watching those absurd Piranha films.
By the way, people eat piranhas. I can tell you they’re not half bad.
The electric eel is notable for being both electric and not an eel it’s actually a species of knifefish. This fellow is actually pretty big, being able to reach up to 2 meters in length. But, of course, its most awesome feature is its electric powers acting like an organic battery, it can produce a shock up to 860 volts and 1 ampere of current. Not enough to kill humans by itself, due to its short duration, but it’s certainly unpleasant.
It also has a really derpy face.
The black caiman is actually the only animal in this list that I’d classify as seriously dangerous. It’s the biggest caiman species and, well, it’s a crocodilian. You do not want to mess with crocodilians. It’s pretty big, with some individuals growing up to 6 meters, though most never grow beyond 4.5 m. Still, attacks aren’t common. Keep a respectful distance between you and them, and you’ll be fine.
Also, humans kill a lot more caimans than the other way around. Just sayin’.
I know this sounds a bit cliched, but humans really are the biggest killers of all predatory Amazonian animals. It’s really hard to stop people from killing even endangered species.