In the Advance Wars series, you can battle on land, in the air, and on the water!
One of the special naval units is the Sub, which has a special command called “Dive” which makes the Sub, well, dive underwater, making it invisible for the other players!
(I don’t recommend submerging these papercraft Advance Wars Subs in water, though… ;o)
Have fun building!
Advance Wars Subs papercrafts