A neat trick I read, and then used in a dogfight with a destroyer (my term for fighting/dodging them at periscope depth- either to attack them or press an attack on their convoy) was to use REVERSE silent. The trick is to go ahead flank just before their pinging ends, so they have a hard time adjusting to your increased speed, but enough time to register it. Then right after you dodge their depth charges with a slight turn to one side, hit slow reverse. What happens is they calculate your waypoint way out ahead of you, as they are expecting you to go ahead at 6 kts or so. Instead, you are going at -1 or -2 knots, meaning you end up making a 7kt difference between their next plot and you! All of that done silently! PLUS, it's the fastest way to make a dramatic change of heading, particularly at quiet, slow speeds. Making a 180 degree turn at 2 kts is going to take a long time. Too long for you to put any distance on that bearing before they come around for another pass.
That's my little trick, and it might very well help at any depth. Having said that, the general maxim of run silent, run deep, and run during mid-rough seas is crucial. Sitting at shallow (100M or less) depths in calm seas is a guaranteed way to die, even early in the war. Deeper depths, rougher seas, all help in varying degrees depending on what year of the war it is. So far, for me, I've had few serious problems evading destroyers as of mid-1941. I'm expecting it to get much worse shortly.
