I was patroling off the east coast of England early in 1940 and managed to sink a lone merchant close to shore( around 35 miles). I had already taken a bit of hull damage ( hull integrity 85%). Soon after this a detroyer appeared and I dived. Now the problem started because I was unable to maintain depth without going to full ahead and this left me with 4 options.
Rest on the bottom (76 meters) this didn't work as I kept getting detected by asdic
Emergency blow and then a burst of speed from resting on the bottom to avoid a depth charge run. Clearly you can only do this so many times
Constantly evade depth charges by changing depth and speed. this doesn't work because you can always be detected and can't maintain depth at slow speed.
rise to periscope depth and take on the destroyer after he has made a run. I tried this but missed.
Needless to say I died.
Why can't NYGM keep a depth at slow ahead but GWX can. If I could have used silent mode I would have shaken the destroyer off.