Warphoenix.....Unplug your computer or I shall be forced to taunt you again!
"Your mother was a hamster and your father smelt of elderberries, now go away or I shall taunt you for a second time!!"
Now that that bit of Monty Python is out of the way, 2D water would be practically impossible to add subs in. I'm assuming that the way it's programmed now is that the water is an absolute point (hit it with x much force, plane is destroyed), which also throws in another monkey wrench as a negative value couldn't be assigned. The water would have to be completely reprogrammed/drawn for an above water view, and below, along with allowing pressure to grow on the outside of a sub, damage to the sub from pressure, etc... etc...
It could be done, but it would take ALOT of work and some serious time to do, as, if my assumptions are correct, 1) Collisions with water would have to be redone. 2) Water would have to be remade. 3) A new damage model would have to be put in place (not arguing!
) and 4) A way of destroying subs would have to be made (ie depth charges w/ task groups).
I love the idea of subs, but it would take a bit of work...