A sub would be very nice, but in order for that to happen V-Step would have to model the world below the ocean and would probably cause lag even if you're in a classic surface ship. Remember that undersea mountains, valleys, and rifts would have to be added, as well as the underwater portion of icebergs and maybe coral for Bora Bora. Also it gets dark underwater and the current light system on ships is just dots of color. But if subs are ever added it would be cool is shipwrecks would also be modeled so you could have exploration journeys (maybe the Titanic in the Atlantic Ocean map?).