There was a German torpedo built during WW2 (can't remember it's name) that used a V8 and consumed it's own exhaust gases, boosted by oxygen held under pressure in the torpedo, thus giving no bubbles. Very impressive for it's time, even given the limited operating life (!) though I'm not sure what it would have done to buoyancy during the run........
I believe it arrived a little bit late for service, but did well in it's trials.