[Sailor Steve]

One thing you can do is what the Americans called the "End-Around". Wait until they are on the horizon, surface, go to flank speed and head at a angle to them, so they are always on the horizon and you slowly get in front of them. Depending on the situation this can take a day or more, so you have to be patient. Then you'll be in front of them so you can make a decent attack. Sometimes it helps to dive and get a good sound bearing, then surface and take up the chase again.

Another thing you can do is approach as close as you dare, making the final run in on the surface after dark. This could work in real life, but the game can be finicky about how well they can see you at night.