U-Flak is fun. The patrol after I got the 3 x twin M42s I got 65 aircraft. The renown paid for a lot of homing torpedoes
I had lots of high-ranked flak gunners (gotta allow for attrition), tell them to fire at long range at only incoming aircraft. The biggest threat is from flaming Sunderland kamikazes. The rapid fire 37mm is death on small ships too. 100 rounds to sink a coastal merchant sounds like a lot until you realize it's like 25 seconds of fire from one twin mount.
It seems reasonable that as long as you're cruising on the surface near the coast during the day you'll be under constant air attack. Go submerged for a while and change course to get a bit of breathing room.
Daytime is for flakking, night is for travelling
