I have had the experience several times of having a naval unit just vanish, only to discover by carefully going through the turn report that "the .50 fleet bombarded Fort Whatever, inflicting 8 hits and receiving 293 hits in return". As the side whose fort did the bombarding, I get even less information since I don't know if the ship vanished or not. It would be nice if at some point a patch could give us a way to get a little more information. Presumably if our fort sank an enemy ship we'd know about it.
The same thing applies to naval combat in the sea boxes. "Semmes command found 6.Fleet while patrolling, inflicting 8 hits and receiving 4 hits in return" would be a lot more useful if you could look at a battle report and see if any of Semmes' victims were sunk. Maybe in the high seas you would have some chance of not knowing.