The United States Navy maintains a number of its ships as part of a reserve fleet, often called the "Mothball Fleet". While the details of the maintenance activity have changed several times, the basics are constant: keep the ships afloat and sufficiently working as to be reactivated quickly in an emergency.
In some cases (for instance, at the outset of the Korean War), many ships were successfully reactivated at a considerable savings in time and money. The usual fate of ships in the reserve fleet, though, is to become too old and obsolete to be of any use, at which point they are sold for scrapping or are scuttled in weapons tests.
