That would be silly, right? Hence the joke. I don’t really mean to ask about that, it just seemed a more inviting title than “What kind of seal is there where the propeller shaft exits a submarine ?”
The way I understand WWII submarines, there is a shaft that exits the submarine and connects to the propellers in the stern. Since the other end of the shaft has to be connected to either an electric motor or a diesel engine, that part of the shaft can’t be immersed in water all the time. Thus there has to be a seal that allows the shaft to rotate freely, but keeps water out.
How is it done on deep diving Subs like Alvin? My guess is that the prop is connected only to an electric motor. The motor can be immersed in water. There is a cable that goes from a dry part of the sub to the (wet) motor, but the cable does not move, so the seal can withstand more pressure.