[Crannogman]

I usually treat it as though the ship is traveling along 2 parallel courses and giving equal time to each. I try to base my target solution upon the closer track, and accept that the ship's effective speed is different from its raw speed thru the water. Of course, you have to time it for the ship to be on that track when the torpedoes get there. IRL this wouldn't work b/c the zigs are more random, but the game's mechanics in this regard are quite predictable