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.
After the Second World War, with hundreds of ships no longer needed by a peacetime navy, each fleet consisted of a number of groups corresponding to storage sites, each adjacent to a shipyard for easier reactivation.
Many of the deactivated World War II merchant vessels were of a class called Liberty ships which were mass-produced ocean-going transports used primarily in the convoys going to/from the U.S., Europe, and Russia.
Most Liberty ships when deactivated were put into "mothball fleets" strategically located around the coasts of the U.S., or sold into commercial service.
Vice Admirals Herbert F. Leary and Thomas C. Kinkaid served as Commanders, Sixteenth Fleet, after World War II.
The groups of the Atlantic Reserve Fleet were at Boston, Charleston, Green Cove Springs, Florida, New London, MOTBY/New York Harbor, Norfolk, Philadelphia, and Texas.