from ERNST SCHMIDT (10-+-1983)

submerged U-Boats used battery driven electric motors and could travel only about 60 miles in 24 hours before the batteries ran flat?

it took two to three hours to re-charge the batteries to full power? The electric motors were now used as generators.

at 500 feet down, some sixteen tons of pressure per square foot are pressing against the submarine?

the fuel tanks on German U-Boats were open at the bottom so therefore, it floated on its own oil?

torpedoes were like miniature U-Boats? They were driven by combustion and compressed air while the later models used batteries and electric motors.