I think the current version of Dark Batleboats isn't all that "dark". You still get to see the board of your opponent.
Here's a variation I know that seems even darker (and more challenging):

- each player gets three shots in turns
- after each round of shots the player is told how many hits he got and the type of ship that was hit . But he's not told where the hits occurred (of course you know it was in one of those three positions but you don't know which one). This is often played with a pencil so people can mark possible positions and unmark them once they are sure that the shot wasn't in a given spot. Other players have the boats drawn on the side of the board and start marking away the squares to know what they've hit so far.

So instead of just guessing the direction the ship is in you also need to guess it's actual position first. As a matter of fact you often finish the game without knowing exactly your opponent's board configuration (who cares where the enemy was as long as he's down with the fishes? :))

This version of course takes slightly longer to finish but is far more chalenging because you must be much more attentive to the game than in the standard variation. As a way to compensate for the great amount of luck usually involved in battleboats :)

So does anyone know this variation? what do you think of it? (it's actually easier to play than to explain)