Wired... - Damage question

Hi,

explain me something... I'm testing longer repair time mod as there is a problem with saved game when being damaged (instant death). Tweaking the file I wanted to test it and in my campaign I stopped 300km from Bergen - very dangerous place because of plains.

None could find me, if even than he just passed by, one tried to attack, not a single bullet hit or bomb... eh ok head for lervick, full flank. I managed actually to get into the port!! Bunkers were shooting too high, DD (which hit land as usual :/ ) was shooting with everything, even throwing potatoes! Finally a someone managed to hit and I could test it... Tell me why I do my best in normal career to avoid contact with airplanes and somehow they drop bombs with surgical precision! And now this?? Wired... now I know why DDs are quite simple to evade...

Main Q:

I understand that DC were not that strong and simply a wave of pressure was damaging the boat but a direct explosion from the DC would be deadly. Same with bombs? A bigger air bomb should sink an U-boat instantly? Direct hit from a DDs cannon would also perforate the hull as I suspect. So any form of direct hit would cause serious damages, casualties and probably want allow for a dive. Do I think right?

I don't understand the model completely yet, but I know one thing. It works - I'm loosing my socks when I see an incoming bomb and I'm still too close to the surface.