You should only have to patrol within a certain range of the icon for a few days. You don't necessarily have to go pinpoint to it. Use your compass to make a big circle with the icon at the center. Expand it out to area equal to required patrol icon, and just cruise through there for the required time allotted.
Also, if you are playing with limited fuel, watch your speed, as you need to be able to get back to base, as they don't send out ships to tow you into base, or tenders to refuel your sub.
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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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