Updates to water graphics and mechanics. Things such as clear water options or the ability to colour water to showcase underwater scenes or details.

A bit more difficult but water physics that allow for waterfall placements.

Maybe even a custom water type that has waves crash in intervals for beach themed plots.

And finally the ability to customise the heigh of which the water starts, with the current pools the water surface is slightly below ground level which is good for a pool, but no everyone uses the water for pools!