It mostly depends on your sonarman's experience. The more you seem to pick up at greater distances, the more attuned they get at reporting sonar contacts at further and further distances.
The other thing to watch for in heavy traffic areas, is not to fall for the ruse of the lone merchant vessel sailing through. If you sink them too, the bigger groups tend to stay away. Same goes for the lone destroyers. And I like to take them on. They are a real challenge sometimes. Especially a down the throat attack. With practice, it can be done with one fish, but them the entire area is alerted to your presense.
Also in heavy traffic areas, you can be choosey about what convoys or TF's you go after. I tend to let the ones with smaller vessels pass. Getting 2 or 3 big tankers on the list of sunken ships gives better ratings after the patrol is complete.
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A legislative act contrary to the Constitution is not law.
-John Marshall Chief Justice of the Supreme Court
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