Glomar ExplorerApril 11, 1968, the Soviet Gold-class ballistic missile sub (SSB) K-129 sank near Hawaii, and after it became evident the Soviets did not know the location of the wreckage, the CIA tasked itself with Project Jennifer, an effort to recover not only the wreckage of the sub, but the code machines, book, and other intelligence to be found therin.
Citing Andrew Toppan's sci.military.naval FAQ
The CIA ran an operation to recover the sunken submarine. The recovery effort centered on Hughes Glomar Explorer, a 63,000 ton deep-sea salvage vessel built for the progect. The ship was built under the "cover story" that she was a deep-sea mining ship, intended to recover "manganese nodules" from the ocean floor. The ship was supposedly being built for the Summa Corporation at the direction of Howard Hughes for use by his Global Marine Development Inc. At the same time the "Hughes Mining Barge" was built. The barge, commonly known as HMB-1, was a submersible barge intended to carry the "claw" to be used in the recovery effort; it would also be used to hide the recovered submarine.
For specifications and further info, see also: