All passively cooled thin highend phones can't run highly loaded games longer, due to GPU makes massive heat, so actually fan is practical for such use case.

Wouldn't a water cooled phone be much more awesome?

"Water cooling" is just a heat transfer method, so you need water, pump and external fan or large heat sink. I believe just a fan without water is enough unless you're LTT.

Possibly you mention about some manufacturer that advertises vapor chamber as "water cooling". I don't like their advertisement because it's just a improved heat pipe.

Wow, you know what water cooling is. The next step is that you need to read up on building gaming rigs and understanding that setting up water cooling for cell phone is just the right level of absurdity.

I mean it is literally the "Republic of Gamers" phone