Wizards of the Coast will be releasing the Axis and Allies Minis: War at Sea Surface Action expansion on October 25th, 2011. Each booster sells for $15.99 US. From their announcement:
The War at Sea: Surface Action contains 40 authentically detailed miniatures that war gamers, WWII enthusiasts, and collectors can use to assemble fleets with which to do battle on the seas of World War II. Battleships, cruisers, submarines and aircraft will help you bring the battle to your opponent. The War at Sea: Surface Action lets players add to their existing navies to recreate historical or "what-if" battles that rage across massive 30"x 40" battle maps."