I am not sure if this has been suggested before (I did not see it when I searched just now) but I have just finished taming my own piece of water by putting it in a cube (as seen in the screenshot) and I was thinking it might be nice to be able to drain water from the cube. Not sure how difficult this is to do but if it was server intensive I could be happy with an optional module that works similar to the mining units (only works on active tiles). I also think making them drain by default would