Submarine disaster drama made under the auspices of Mussolini's department of defense. During maneuvers a submarine collides with a surface vessel and drops to the ocean floor. The crew have thirty hours' worth of air to get it back to the surface.

A down-on-his-luck apartment house manager hatches a plan to rob a Catalina Island bank and escape with his accomplices using scuba gear.

About U-Boat 39 the first U-Boat sunk in WW2 by the UK Carrier Ark Royal.

A submarine coming into port is seen gliding smoothly on the water and the little rowboat which is to bring the captain of the vessel to his post is seen leaving for shore. We see the dashing young officer bidding his love adieu, and then seating himself in the frail craft is soon once more on duty at the wheel. Away they go, and reaching the wide sea the ship gives a lurch and disappears under the water.

Italian documentary on submarines.