Has anyone tried to make a sub that can go under but has a small BB gun on top? I can see people surfacing, shooting, being shot at, and submerging.
And you can't shoot them either. Honestly, submarines are little fun for the massive amount of work they take. You would enjoy yourself much more in a cruiser, trust me.
I posted some pics and videos of Frank Falango's I-400 a couple of years ago. AFAIK, it's the only combat-capable sub currently in operation. <Click on pic, click on right arrow to advance to next pic>
He uses a powered screwdriver, so probably not as long as you'd think. That being said, I think even Frank would agree they are a novelty which are only fun for those who like engineering impractical things.