Vessels with military utility or logistic value are held in retention status and are in a preservation program that is designed to keep them in the same condition as when they enter the fleet. The internal spaces are dehumidified to slow the corrosion of metal and the growth of mold and mildew. DC power is distributed through anodes to the exterior underwater portions of the hull, creating an electric field that suppresses corrosion and preserves the surface of the hull. External painting and other cosmetic work are generally deferred since they do not affect the ability to activate and operate the vessel.