Subs would be cool. And yes, I remember Silent Service. One problem tho, there's a whole lot of problems. Which submarines would you add? Which type torpedo and guidance mechanism? Would they allow for rogue torps? (When the guidance failed and the torp did a circle back to where it came from) What about the dangers to a sub? Crush depths, sonar, audiophones on the sub-hunters, AIR SUPPLY (no reference to the band), fuel and battery. You would have to completely remodel the water so it isn't a blue parking lot. Now you have sea affects to worry about. High seas would obstruct views thru the periscope, which it should, but from the computers end, how much more proccessing power would it take when you're flying and the computer's busy trying to figure out where each wave went? You would have to build a whole new game essentially, (Aces Deep) Then figure out how to combine the 2 without sapping all the power from the computer.