For some reason patrol won't end [SOLVED]

[Corporal]

When the mission is patrol area, ie Celebes Sea, I motor my way down there, float around the icon for a while, sink some shipping, refit at a nearby port, go back a gain and kill some more ships but it still says mission incomplete, what do you have to do to satisfy the mission criteria?

[TDK1044]

You need to stay in the designated area (not just the icon) for a period of 24 hours. Set some waypoints and hunt for kills for 24 hours and then you can return to Base and end your mission.