Allocate water to specific tiles

[eycore1]

Instead of having water/no water for the whole room. For example, this would be good at the start of 40 fathoms, where the entire starting area is unflooded except for the bit going down (they are in the same room). https://i.imgur.com/RgZnUEp.jpg

[rr-]

This requires heavy changes to the engine as the water level is a flag tied to the room, so you'd have to dissect the room into smaller rooms and recompile the portals.