That probably should have counted. You'll need to sink one ship near the yellow patrol area to get credit for that, but the thing that sober posted should have filled up if you basically sunk them anywhere along the east coast there.
I've unfortunately not completed this first mission in my 7 campaign restarts since starting again last week, so can't remember exactly how to finish that mission. Maybe it's date locked? Like the next one can't start till X date so it won't let you finish the first one?
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