[seafarer]

Is this stock SH4? If so, I found that a number of times - nothing to lock onto to get my required photo's to finish the mission. That's one of the reasons I very quickly went to the major game play mods (TM and RSRD in my case) - to get rid of the photo missions altogether. Aside from being ridiculously unrealistic, they often just cannot be completed anyway.

You can either hang around hoping something shows up, or sail on out and get back to hunting and sinking enemy ships. You won't get credit for the photo mission, but you'll still get renown and credit for a successful cruise if you go off on your own.