The National Defense Reserve Fleet (NDRF) was established under Section 11 of the Merchant Ship Sales Act of
1946 to serve as a reserve of ships for national defense and national emergency purposes. It is a different entity than the
United States Navy reserve fleets—the NDRF consists primarily of merchant ships, while the Navy version consists of warships, however the NDRF does maintain under federal contract, a flotilla of warships in reserve status for the Navy.
See more at Wikipedia.org...