The Defense Logistics Agency often sells decommissioned navy vessels to civilians through their DLA Land and Maritime section. NavySurplus.com also sell decommissioned naval vessels, and there are naval vessels from a variety of companies listed on the Apollo Duck website.
The DLA maintains a program known as the Defense Property Disposal Service, which assists the United States Navy in managing surplus property. Some decommissioned vessels, such as destroyers, carriers and submarines, are either scrapped completely or placed in reserve for the Navy. However patrol boats, minesweepers and other small craft are available for purchase by civilians. The DLA usually requires civilians to complete the Classes of Surplus Personal Property document to initiate the process.