This matched pair of visually spectacular Royal Navy instructional films titled U-Boats Recognition and Attack by Naval Aircraft were released in 1941 to detail the workings of submarines and techniques of anti-submarine operations for trainee Fleet Air Arm pilots.
Part 1 is titled Recognition. It explains how to identify the three main types of German submarines before detailing the basics of the engineering behind them in order to explain their limitations and weaknesses.
Part 2 is titled "Depth Charge Attacks by Naval Aircraft". It talks viewers through the techniques used by Fairey Swordfish crews to locate, track and attack a U-boat with depth charges.