On/in people you care about

... on, or in, people you care about.

In this universe, pee is usually either tasteless or tasty, completely sterile, as warm as in ours, and only a bit less intimate; thus, it's become the norm to show someone that you care about them by involving them with your pee.

Wet hugs are very much a thing, as are pissing on someone's food to give it more flavor or waking them up by peeing on them. You could compare it to kissing someone, or giving them a very loving hug - whether platonic or otherwise.

Of course, if there's no one around and you really can't hold on, you're supposed to go on yourself. If there are only strangers around, you should ask politely to use them as an urinal before wetting yourself - it'll probably be awkward whether they say yes or no, but it'd be even more awkward to wet yourself without asking first.

As you may have inferred, this also means that society as a whole is more tightly knit: it's very rare to not be near someone that you care at least a bit about, be they colleagues, loved ones, family or friends.

Alright, I think you're pretty much ready to go. One final thing: do not look up to the stream."