Yes, I agree it is a cat and mouse game, but then?
I shallow waters I must try my best to kill the destroy first before it finds you.
Once it finds you, you are DOOMED and prepare to go to hell
/heaven
. Well, what I do is to attact it to come close to me from the bow / stern side. Then, when it is 500m away from me, I set and launch 2 torpedoes with appox. 4.25m as a running depth with magnetic detonators on.
The destroyer usuall try to follow your course so you cannot hear them clearly through hypophone and let you run into their following charges, so you will face its bow side, which has a sharp surface and not suitable for impact detonators.
Let themself run into the traps. They usually get killed when the fish explodes under their keel and they are not fast enough to change course
(they need a reaction time!) even they knew two fish is running straight to it. Get meant.
If I want to save fish for later attack, just lower your periscope, rig for silent running and sneak away
