Personally, I'm mad about hit and run strategy. Means attacking convoys at night with the boat surfaced and using very long shots, similar to the night raid scene in Das Boot. It was also the favorite strategy used by Otto Kretschmer. Once I track down a convoy, I shadow them until midnight then i get into the position at max distance and unload. Depending on the weather conditions, I use clear targeting or blind salvo then turn the sub and run away. When things calm down, I resume the pursue until I unload all my ammo.
Attacking a convoy from inside with acoustic torpedoes is also great fun. Playing mouse &cat with the mad escorts and sinking merchants at the same time it gives a great adrenaline rush. But once the ammo is depleted...
