Piranhas have dozens of uses. Food, bait, aesthetics/decor, pranks, weapons of surprise, scissors, evil lairs…

It's a great threat

also it's food

Step 1: Collect a bucket of piranhas

Step 2: ?

Step 3: Profit

I'll just pop a quick "P" on that so everyone knows...

Don't forget how to put yourself out if you spontaneously combust, and acid rain.

Fish are food, not friends

They look like they are 90% gristle and hatred.

Wikipedia claims they're quite popular.

They taste like fish. I'm not joking.

So much so that they're illegal to fish in parts of the Amazon because they've been nearly fished out of existence

But that’s what the cartoons showed.

Brazilian here. Perfectly safe (color-wise; of course it can be polluted as hell despite its color, just like any other river).

Our ground/mud has a different color. Some areas on the south even have a red soil (very fertile, but makes everything about ground level look dirty very quickly): https://en.m.wikipedia.org/wiki/Red_soil

There's great variety of water colors even in the same area, just search for images "meeting of the waters Manaus":

Water can be like this when it rains a day or a couple hours before. Every river become like this when it rains. It is perfectly fine to eat fish from this river.

Don't they usually set up a sting and invite them out on a "date" where they're then confronted about their lies and posted to Youtube?

As long as you're not bleeding or anything, you could safely jump in the water and swim with them!

They probably do