Back in my day that sub was called r/ WaterNiggas but as it gained popularity, they changed it to something less...in your face. The original meme was kind of an ironic play on how water tastes vs how it's necessary for life. That's the whole joke. "damn this water actually kinda fire???" well of course it is, it's what sustains life on this earth.

There was also a specifically black sensibility to the original joke, playing off a cultural stereotype that black people don't drink water, in fact they drink anything BUT water--soda, grape juice, energy drinks etc. Mostly just a stereotype, but I remember when those memes started circulating a lot of them came from "black people twitter"

It has since devolved into a subreddit for hydration and potable water appreciation ....and that's fine too. But the real ones remember the water niggas