Thanks, chaps. I was ready to give up until today. 10 hours of combing the North Sea and nothing to show for it, until I got a ping. Then another. Turned out to be a convoy of 10 merchant ships. I couldnt believe it! I immediately saved the game so I could practice hitting moving targets for once and eventually had to come up to use the deck gun to sink the final five.
I noticed that when the "ghost ships" would show up as battleships, they seemed to be spinning around like a fruit fly. I assumed it was their radar. Silly me
