I don't know how much of the original team are still available for this kind of project anymore. What you suggest is not actually a small modification. I can't remember if it is possible to place an underwater lot in UC in-game, but if there is nowhere deep enough, then editing the map to do so poses all sorts of problems. Anywhere the terrain is altered at all can cause tears around lots, and from my experience, it doesn't even have to be near the edited area. Also, you would need the original file before the population was added. Otherwise they would need to be removed and then added all over again. It's a LOT of work.