Room Filling With Water Effect?

[The chaser]

A primitive plane nope, but you can with an animated model. Explanation:

Create a 3D model which is just a plane, and add the water texture. Then, animate it so it goes up. Done.

Then, in your level, create lots of liquid areas, one for 0.5 unit aprox and disable them. All of them. Then, make a script that enables them as the water rises and you're done.

Obviously this is the simple explanation, the "how to proceed". If you need more details, ask :3