Flower Corvets
 

How do you deal with them? I have a few times surfaced and gave one a couple rounds from a deck gun, it seems to scare them off. I didn't want to waste a torpedo, and it was the one type of warship a submarine can win against in a surface slug, but I also tried to stay out of the firing angle of his gun.

Once in awhile I will come across a convoy with nothing but flower Corvettes. What I do is stay on the surface attack at night. I then use my speed to get away from them. If they pursue me, I make sure to show them only my stern. They will eventually lose sight of me and give up.