Finally got through Convoy Attack training last night - er, more like early this morning - without losing my skin, my crew, or my boat.
Took out the rear escort and the tanker before having to go deep and silent when the other escort circled back to see what all the fuss was about and proceeded to let me know I'd worn out my welcome in no uncertain terms.
Managed to avoid all but one depth charge run and then took some hits, ended up about 136 m down while waiting for damage repair and flooding control. Then played cat and mouse with the escort again until I got so tired it was either pack it in for the night or come up and try to take her out or hope for a miracle escape-wise.
After several narrow escapes and a couple crash dives, managed to come up to attack depth just as she was for some inexplicable reason turning right across what would in about two seconds be my wake and only a couple hundred meters behind me. Oh, stern torpedo tube, how I love you. And it was the only tube I still had a fish in! Fired my one available torp and then took off, intending to just get the heck out of there until I knew how much damage the hit would cause.
Don't know what I hit on her but it musta been the right spot, cuz she was done. Caught up with the remaining four merchants, now unescorted, with only four eels left. Did as much damage as I could do with those and then finished the job with the deck gun.
If only I'd clicked "Exam" when I started - but at least I got through it and I certainly learned a whole lot about running silent, rpm control, when it's safe to rev it up a little and when to dial it down again.
Feeling a lot better about the prospects of getting the job done in game now - still a lot to learn, but having survived being hunted once and living to tell the tale sure does feel good.