There are several techniques to do this. I usually do hydrophone sounding every 20km, traveling at 2knots. There is a video out there somewhere in the download section...I think. The video in itself shows how to do hydrophone tracking by using all of the map tools. Very interesting. I have been able to make it work a few times. Granted, it is tough, but if you get 1 kill with this type of method, it is very rewarding. See link of basically the same question. Look up the name
"Nefelodamon"
http://www.subsim.com/radioroom/show...ght=hydrophone