Hughes Mining Barge, Submersible barge in Alameda, United States

Hughes Mining Barge is a submersible barge about 99 m long, 32 m wide and over 27 m tall, now a covered floating drydock moored at the Bay Ship & Yacht Company yard on Main Street in Alameda, California. Its dark hull section carries a continuous row of arched tan roof segments, with a flat dark gray panel standing vertically at the right end and a blocky building section with a ground-level opening at the left.

Built from 1971 at National Steel and Shipbuilding in San Diego Bay for the CIA's Project Azorian, the barge hid the capture claw used to lift the Soviet submarine K-129. In 1973 it submerged near Catalina Island so the Glomar Explorer could take the claw aboard. Mothballed in 1974, it became a floating drydock for the Sea Shadow from 1982 to 1986, and was sold in June 2012 for $2.5 million.

The name comes from Howard Hughes's Hughes Tool Company, the cover story used to explain the barge and the Glomar Explorer during Project Azorian. The barge's role stayed secret until the operation was declassified, and it later hid the Sea Shadow, tested only at night.

The ship can be viewed from outside the Bay Ship & Yacht Company grounds but is not open for public access. It sits on the western shore of Alameda Island, across from San Francisco Bay.

A moving roof system allowed large objects to be lifted invisibly from the water surface into the interior. This design made it possible to carry out operations without observers seeing anything from outside.