Recently I've spent a lot of time rewriting water system. The new system just pathfinds from the outlet to the sea and fills every pool it encounters on the way. It's a bit weird, bc the player can flood a huge pool in a single frame, but I think I can live with this as there's so many advantages: it's a lot faster, allows for really crazy watering systems, much simpler to render and makes more sense with fast forward.
@johann this gives me a ton of original tomb raider memories