I too use Trigger Maru and was getting wiped out every time by destroyers. Every time I heard the screws of a destroyer out came the "depth charge medicine" (you owe me a few bottles of whisky Ducimus
)
I found my game play starting to change where I would seek out unescourted ships and shy away from convoys, virtualy ignoring contacts sent onto me. After a few patrolls like this I had built up a pretty good crew what with medals, experience, etc and one night coming onto a merchant convoy I decided to try my luck once more. Well, once again the destroyers were over me like flies on horse s..t. I had saved the game AFTER I had launched my torps. I kept reloading and trying again because I really didn't want to start a new career and lose this uber crew. After trying to battle surface and get away using rear mounted deck gun I failed. Trying to get in under the convoy I failed. Trying to shut down everything I failed. Trying to creep away on silent running I failed. And then on the 4th attempt I found the trick. I was in deep water so what I did was dive way down to past crush depth (my boat was still sound with no damage) and with my sonar man giving me readings constantly, engines going from off to standard to 1/3 depending on circumstances I fluctuated my depth in accordance with the run the destroyers were making. In other words I timed it that I would be coming up fast in time with the destroyers pass over me and then once those cans hit the water I would dive down again. Better to have the cans following you down than you coming up to meet them
. Using all these tricks plus zig zaging, shutting engines down, silent running and using decoys (though I think those things had no effect whatsover and in future I'm not going to use them again) I actually got away after many hours of game time. I felt truly elated and the scotch never tasted so good.
I beat the A1 destroyers a second time this morning before coming to work. I kicked on the computer fired up the game and here I was following a merchant convoy running parralel to it just within the horizon. Game time was early morning. I was unsure of how to attack it (still nervous of those destroyers) and thought I would rather shadow it until night fall. So, I took her down to 100feet set silent running and decided to go take a bath before getting dressed for work. I've got the sound up and I'm not more than ten minutes into my bath and I hear that dreaded pinging coming from my bedroom. I think but how can this be! When I get to the screen I punch outside camera and true enough there are 2 destroyers above me. Then I notice away in the distance something small bobbing about in the sea. I take the camera in and yes, its a life boat. I look towards the convoy and see it is at least one ship light. So another cmdr attacked and I'm caught up in it. This game really is well thought out I will give it that. So again, using previous tricks newly learned I survived and got away with both periscopes totalled, deck and aa guns damaged. But I lived. So it can be done.
So, as one becomes more and more proficient as a cmdr one's chances of success increases. Of course I don't do crazy things like take on the destroyers with deck guns, or even for that matter make them my first target. I will now only tackle a destroyer if there is no alternative action open to me. And of course I never attack in shallow water.
My suggestion to you is save your game AFTER you have attacked so that is always the given point where you are committed and replay as many times until you get it right at getting away. It is a learning curve that will stand you in good stead later on so don't think of it as cheating but rather as training. Of course once you have learn't erase from your mind where the "save" button is