The same designs are used for warships as for other ships. Galleys are much more commonly used for war than for trade, though, and compromise the majority of the fleets of the Confederation and the lands of Terra Centralis, though the Confederacy also depends heavily on its leviathones. The Free Kingdoms depend mainly on sailing ships for their navies.
Clemencia and the Free Kingdoms use a system wherein coastal settlements are obliged to provide vessels for the kings use, some months every year. The Confederacy and the Cargan Empire have standing navies.
In times of war, it is common for merchant sailors and vessels to be hired or commandeered into the navy, to bolster it.
In past times, war galleys were universally equipped with beaks, to ram and sink enemy ships. This weapon has gone out of fashion, and now it is common for most warships to instead have a proscobis under the bowspit, accessible through and guarded by the ship's forecastle. Some galleys, many in the Confederacy and almost all in the Cargan Empire, still have beaks.
Artillery is mainly placed in the forecastle, aiming forward. Forecastle artillery is aimed mainly by pointing the ship in the direction one would shoot. Large ships, such as carracks and heavy galleys, may have similar equipment in the aftcastle as well.
Some ships have experimented with additional pieces of artillery on the deck between the castles, shooting more or less perpendicular to the ship's axis. However, problems with recoil and top-heavy ships means that either such pieces are small (typically scorpio or onager ballistiae) or the ship has a drastically reduced seaworthiness.
Artillery in the castles may be cannon, catapults, ballistiae or fire-siphons. However, cannons have come to be the most common kind of artillery there.
Despite the advance of the cannon, the quickest way to destroy a ship is often to burn it to the waterline. Incendiaries of all kinds are widely used in naval warfare.
The ultimate incendiary, used in naval battles. The upwind side releases one or more burning ships towards the enemy, aiming to make them break formation and get confused, hoping to set one or more of their vessels on fire.
Marines are armed much the same as their counterparts on land. There are two important differences however.
Even heavily armed and armoured marines favour one-handed weapons, as weapons like flails, two-handed and bastard swords require to much space to swing to be useful in the cramped quarters of a ship. The favoured sword is the cutlass, which is excellent for close fighting and inflict grisly wounds.
Secondly, gambesons (padding worn under armour) tend to be made of leather rather than cloth. This is due to the humidity at sea, which can make highly absorbent material unbearably heavy rather quickly. However, leather gambesons are rather clammy.
Maneuvering is of paramount importance. Captains strive to keep the sun and the wind at their stern, so that the enemy has to cope with headwind and glare. Furthermore, it is favourable to be in open sea, with maximum room to maneuver (and to flee, should it prove necessary).
The sides of ships are the most vulnerable section, and the prow is the most powerful (making it very undesirable to "cross the T" Age-of-Sail fashion).
The attacker launches artillery fire, either to sink the ship or to decimate the men on it.
If boarding is desired, one closes, stern first, and tries to grapple and board at the side if possible. Cannon-bearing ships almost invariably fire a load of grapeshot right before boarding from the prow. Boarders are covered by missile fire from the forecastle, which is usually a melange of arrows, bolts, javelins (particularily in the case of Cargans), bullets (ditto for the Clemencians) and sometimes even rocks.
The defender tries to turn his prow or stern to the attacker, and if this is impossible to catch the boarding party in crossfire from the fore and aft castles.
Prior to a boarding action the defender (and any prudent attacker) will have set up barricades to form lines of defence from prow to stern, and fighting will be from barricade to barricade. Tales are told of how a valiant sallies from aftcastles have save ships that seemed doomed.