Just a simple problem I think, but I might as well mention it.
http://img.photobucket.com/albums/v194/BwdYeti/Sub_what.jpg
I had the unit display on and saw the little icon it showed for a Destroyer in my land was an Attack Sub. The Destroyer appears to be injured so I'm guessing the Attack Sub hiding under it has more attack and becomes the unit the unit icon displays. And I don't have my own Destroyer or anything nearby, so I definitely shouldn't be able to know a Sub is there. (Notice only one little white dot next to the Destroyer's flag)

This is with the lastest unofficial patch.