I know this probably sounds kind of crazy but is there any way to create actual flowing, physics controlled water than has a fixed volume? So that you could have like a lake and then break open one end and let the water start flowing out of it and eventually drain the lake?
Yes it is possible, but you would need to write your own simulation and that would take a boat load of time. And I don’t know of anyone who has done it with Unity, but you could implement it yourself and then sell it when you are done.