I strongly disagree with your comments on SH3 aircraft.
Coastal Command did indeed operate the PBY/Catalina (and also the Liberator and B17) . In fact a few months later than shown in your video it was a Catalina (being flown by a "neutral" US aviator on exchange) that regained contact with the Bismarck as it made for Brest. The PBY was famously slow, so plenty of time to dive.
The problem with a bomb is that if it is reasonably powerful it has to have a delay fuse to protect the dropping aircraft, which would mean it would explode too deep unless it was a direct hit. Depth charges replaced bombs but it was found fairly soon that using any settings other than 25 feet was a waste of time as the chances of a hit on a uboat that was below periscope depth were too small to worry about. SH3 does not capture this very well and airborne depth charges are a threat at moderate depths.
A uboat was a terrible gun platform and indeed it was found that manually aimed AA guns were incredibly bad at hitting anything. The Bismarck mounted a large array of AA weaponry (including 12 20mm flak and 16 dodgy 37mm flak) but failed to down a single biplane aircraft in two separate attacks in which the attacking aircraft got close enough to use their machine guns against the battleship. Several Swordfish were damaged, and yes some did break off their attacks. However it is unlikely that a single 20mm would have that effect, In photos I have seen of uboats under attack it is the uboat crew that are hiding from the aircraft guns.
Late war boats with many more flak guns managed to bring down slightly more aircraft than boats destroyed, but the British were prepared to accept this ratio. Most attacks would be a no-score draw. Towards the end of the war a boat that chose to fight it out on the surface was a big threat to a Swordfish from an escort carrier, but the aircraft could wait until the boat started to dive, or whistle up some Wildcats to strafe, or call up the nearest escort. Late war Swordfish were armed with rockets, which helped considerably.
Sadly there's not much that can be done for the SH3 AI. For example the Catalinas did not attack on their first pass because of a known bug with one of the highest levels of crew experience.
Having said all that, great video. Even if you were trolling for footage by not diving during the air attack....
