[Havan_IronOak]

I generally try to set up a constant bearing solution ahead of a convoy then go deep and wait for the lead escort to go by.

Then rise up to periscope depth when the first row of merchants approaches my firing line. I start with the one nearest my firing solution and work back to the nearer ships. If they're all small fry, I can down scope and wait for line 2. Of course, I'm playing with map updates on so it's easier to do this.