I just toasted a whale factory ship and large merchant by flanking ahead and then submerging to creep in from the side as the convoy approached. I aimed to be about 500 meters outside of the nearest lane by the time the first row of merchants passed by. Stayed at 80 meters and 2 knots till the lead escort crossed my bow. Then went to PD and fired a speed staggered salvo to hit the large merchant an the whale factory ship in the next lane. Both salvos hit simultaneously and by then I was already passing 60 meters at flank heading deep into the center of the convoy. Once passing 190 I went to 1 knot and turned to exit the rear of the convoy. Hovered around 220-230 meters till the escorts gave up and admired the 22000 tons in my logbook.
