If you check your starting location on a "real" map of the area, I think you'll find the game deposited you at 0 deg long, 0 deg lat.
This sometimes happens when for some reason it does not know where to place you geographically at the start of a patrol. Transferring from one base/flotilla to another usually has something to do with it but I can't recall if one particular combination of factors has ever been pinpointed as the cause.
