Well, what about a faked fluid simulation for WebGl and the real deal for Desktop. In that, you could generate a fluid simulation and then save it as a permanent animation. That way it looks realistic, but its actually a predefined mesh and animation simulation.
So I was thinking some more on this, and recalled one abandoned porn game did this (faked liquid simulation). It looked like a liquid and flowed like a liquid, but it was a static animation and would play every time the same way. That was the old FapLife game by Likkezg. They ran into development issues and eventually gave up on it as far as I can tell. I think they have it on their main site, but otherwise a place like F95Zone would have it.