Ok...
Usually when nobody says anything for a while, I summarize.
Inklings have muscle tissue that can unhook at the molecular level, like that of a sea cucumber. However, in models towards the center or fluid end of the spectrum of solidity vs fluidity, Inkling muscle is also liked together via ink, allowing inklings to become an ink squid when liquefied, which in turn allows inklings to slip through even tighter spaces than oceanic octopi, store things while swimming rapidly, hide in and swim through ink, and probably some other things as well.
Of course, this also makes inklings vulnerable to substantial amounts of water, which can disassociate ink. Inklings have also evolved to take advantage of this weakness in each other be developing ink with a biological tendency to tear apart ink with different biological identifying proteins. Inklings can apparently change the nature of their identifier proteins, although we aren't sure how much control they have over this.
I'd expect certain parts of the inkling would have more ink than other parts, such as the throat having little (as it needs to be exposed to water regularly).
I now personally believe that inklings are relatively resistant to water compared to Super Mario Sunshine enemies, but splat when falling into large bodies of it due to the shock of falling in so suddenly.
Ink, when left alone for around 10 minutes or so, will evaporate... I suspect that this is less because the ink can't remain in place for a long time and more a biological adaptation designed to prevent leftover ink from rotting or attracting potential predators.
...What else is there to say here? ah, yes...
How am I supposed to properly cherry pick facts if you people are going to call me out on it?
At any rate, I still think Mario wins 1 v 1. A 4 Inkling splat team vs Mario? Eh, probably the Inklings win that one assuming Mario is vulnerable to their Ink. Again, we've only seen how it effects Inklings and Octos. The game says absolutely nothing about how it affects creatures that are not made of ink, so that's completely up in the air.
Well, given the ink's propensity to tear things apart, it might be able to leave a burn of some kind. but even if it doesn't, the ink seems to be able to pull things into it like unrealistically dangerous quicksand found in many comic books and whatnot. If Mario were to jump into the ink with a near empty water tank, he would have trouble getting out...
Interestingly, In Super Mario Sunshine, Mario can't sink into the graffiti, even though everyone else can, and I believe will if you deliberately slide a dirty Mario to spread graffiti to their position... Does Mario have some sort of secret immunity to 4th dimensional fluids?
Come to think of it, in many games, Mario can traverse some (but not all) quicksand by jumping through it. This doesn't seem to apply here, though, as Mario can stand on the graffiti just fine (even when no one else can)...
Edit: For the record, I'm thinking of the brown graffiti found in Bianco hills early in the game, which doesn't seem to be particularly dangerous save the bubble monsters it spawns.
