I think that little tank behind the conning tower is where they add the baking soda...
I bet that a good look inside would reveal a couple of "exercise bikes" hooked up to the prop shaft for propulsion.
"Hashim! Yamir! Pedal harder! The Americans are escaping! Mohammed! Load more baking soda and prepare for Crash Dive!"
During the American Civil war, the Confederates used a submarine called the Hunley against the Union Blockade. It was powered by a hand turned crankshaft
Come to think of it, there is a great deal of similarity