Help me get rid of this damn flower corvette

[Immacolata]

Using NYGM 2.01 in may 1940. I sank 2 large cargo ships in a convoy and went below. I managed to shake off 1 destroyer, but this flower corvette just won't let go of me. I try to keep my arse in his general direction, swerving away so that when he does his post-attack run circle sweep he should see my crew mooning his sonar. But he spots me like we were two air crafts circling another. 100% sure, every time. I change depths and run for it in like 20 seconds, then go to 1 knot and wait it out. PING. Is this normal behaviour for a 1940 crew on a flower corvette out of ammo?

I read somewhere that they "lost" interest at some point. This guy seems ready to marry me, he brought flowers even. How are you supposed to shake such a thing off? Im off the coast of ireland, its about 100m here so I cant go really low... but does that really matter anyway? He is long out of drums, so he just harasses me at this point.