NOTE: With the addition of WDS Forgotten Campaigns the game designers added numerous wrinkles and edits to the naval units of the series. But the navies so rarely make an appearance, outside of the Forgotten Campaigns game, that this lesson is still relevant for the remainder of the games.
The American Civil War could not have ended as quickly or as definitively as it did without the power and skill of the U.S. Navy in choking off Southern ports and commerce. Unfortunately, for fans of Naval operations, no major amphibious battles occurred during the war. As a result we only occasionally see Naval units in our games in a supportive role. If you are looking for specific battles where the Navy comes into action than you need to go west to the actions around Fort Donelson and Vicksburg to find those. But even in other scenarios, like those around Richmond and New Madrid, the Navy makes appearances as well.
Naval vessels are subject to the same Fire Combat rules as Artillery and, basically, act as floating batteries. Ironclads or wooden warships does not matter. All vessels have the same rules as field artillery. Their indirect fire capabilities make them a little more unique, they can also move and fire in the same turn, and they can fire in any direction rather than only the way they are facing. But they can still be fired on from flank and rear with the 40% modifier given to the attacker.
Nonetheless, the games manual gives us little information on how gunboats work in the game and even mentions a modifier used when engaging them – but gives us no example of how that modifier is calculated. The gunboats seem more like an afterthought of the designers and remain a minor and “gimmicky” part of the scenarios we play. But do not try to engage them with small arms or field artillery. If you must fire on them with your guns be sure you bring heavy caliber pieces and situate them on good high ground to reduce the enemy’s effectiveness against you.
An even rarer thing than gunboats are the use of “boats.” This takes place in just a single scenario at Brown’s Ferry at Chattanooga (it may be in others but I have never ran across it). In this scenario some Federal units are given boats to cross the river in. These units are identifiable by having a “B” next to their movement points in their Unit Information Box as pictured below. They may travel over any water hex (using column formation) in their boats. Basically, it makes them an all-terrain unit for the battle.