If I go hiking I will sometimes drink from a stream or spring. I know there's a risk to this and I accept it. If I'm going to be out in nature for longer I'm more likely to use a filter like a lifestraw or boil water.
I know you aren't suggesting it that way but your post made me ponder about it. If you socialize healthcare, you are automatically getting someone that says "oh no you don't, not on my dime, I'm gonna have to take care of you if something happens to you, no, no, no", which is practically a parent. It is probably a conversation that should be had. You rarely see it explored from that angle.
So what's the risk?
Apart from anything else the water's going to be too cold for bacteria.
Flowing water can still contain very harmful bacteria.
That's what I've always thought, and it seems correct, but I'm not sure why that would be the case. Flowing water is more oxygenated which should make it easier for bacteria to survive, than in a still pool of water (getting baked by the sun's UV all day).