SS - Submarine x 12
DD - Destroyer x 12
CA - Cruiser x 6
BB - Battleship x 2
CV - Carrier x 1
And on the carrier:
Carrier Fighter x 6
Torpedo Bomber x 2

Since each counter is a single ship, I was thinking that each counter might have three of each ship, to represent a ship taking damage. So a ship would effectively have three hit points before being sunk.