American Civil War Riverine Actions is a set of free wargames rules for ironclads, tin-clads, cotton-clads and all the fun and unique ships that plied the rivers of the United States during the ACW.
naval
Death On The Seas Ancient Naval Rules
Death on the Seas is a set of free wargames rules for ancient naval warfare. Also, Death On The Seas ship appendix.
Bombs Away Carrier Game
Bombs Away is a simple, three page print-and-play game about carriers in the Pacific.
Naval Action
Naval Action, by Lou Coatney, is a set of free wargames rules for miniatures battles in the World War II Pacific Theatre. The page also provides some markers to use in place of model ships.
1666 Naval Rules For Anglo Dutch Wars
1666 is a set of free wargames rules for naval combat in the Anglo Dutch wars. The game is designed for 1/2400 ships on a 2 inch hex grid. Direct download.