U-Boat Your Life.
Say the secret word and you'll win passage on a Submarine. Did anyone else find it odd that Indy would hitch a ride on the hull of a U-Boat whose primary function is normally to go underwater? I always thought this was a bit of a shenanigans but as per this Wiki it traveled faster above the water than below it and thus it was safe to lash yourself to the hatch with your whip. I certainly hope he overheard the Captain's orders, because that's quite a gamble otherwise!
Did you know that for the external shots of the sub, they rented the U-Boat from Das Boot to do so? Check it out!