Quote Originally Posted by Doug-Thompson
Well, that explains it.

If a spy is selected, you get his line of sight.

If the ship is selected, you get it's (shorter) line of sight.

If both are selected (Ctrl +A), you get the longer (spy) LOS.

Therefore, you should be able to go to your agent screen, select the spies "at sea" and select them that way. Will have to check this out, though. Was it that way in RTW?
You will also enjoy a far, far, far, faster movement rate for your fleets...