There should be submarines for water, water should effect most vehicles by slowing them down,(at the least, as it should actually, at a depth, plain out stop vehicles, but that may not be doable)
There should be a datablock for players that makes them able to go faster in water(effect not usable outside of it of course), should be some sort of fish, sharks, etc.
For enclosed areas inside of water, such as a closed, or doored box, a effect that keeps the water out. That, or a adjustment to a zone that allows things to be made inside of it, and removes water effect.
A adjustment to skis and a tool that allows someone to float on water(skis) and the tool to hook them to a vehicle which would move them forward if the vehicle does, but allows them to go side to side.
Any additional ideas, just add here, but if you know of anyone who could, or if you could, try to create those. A thing or two may be copied from other forums, but as those forums are dead, I doubt it matters.
