Well, that depends on what kind of level of game you're thinking.
I, for example, thought of something like this.
You imagine you want to attack an enemy position, and you do it in the rearguard, so why not do it by the river?
I've been checking Global.lua script, but related to water only found two functions.
HideWater() and ShowWater()
However I am sure that TGC development team, will provide whith important and useful functions.
some of them come to mind, such as....
UNDERWATER=X
PLRUNDERWATER=X
AIREQUAL=X
AIRGREATER=X
AIRLESSER=X
WATEREQUAL=X
WATERGREATER=X
WATERISON=X
WATERLESSER=X
ADDAIR=X
AIRON=X
And many others related with the water.
3com