Glomar Explorer

GSF Explorer, formerly USNS "Hughes Glomar Explorer" (T-AG-193), was a deep-sea drillship platform built for Project Azorian, the secret 1974 effort by the United States Central Intelligence Agency's Special Activities Division to recover the Soviet submarine "K-129".
Construction.
The ship was built as "Hughes Glomar Explorer" in 1971 and 1972 by Sun Shipbuilding and Drydock Co. for more than (about $ billion in ) at the direction of Howard Hughes for use by his company, Global Marine Development Inc. It began operation on 20 June 1974. 
Hughes told the media that the ship's purpose was to extract manganese nodules from the ocean floor. This marine geology cover story became surprisingly influential, causing many others to examine the idea. But in sworn testimony in United States district court proceedings and in appearances before government agencies, Global Marine executives and others associated with "Hughes Glomar Explorer" project maintained unanimously that the ship could not be used for any economically viable ocean mineral operation.
Project Azorian.
The Soviet diesel-electric submarine "K-129" sank in the Pacific Ocean NW of Hawaii, on 8 March 1968. The USS Halibut identified the wreck site and the CIA crafted an elaborate and highly secretive plan to recover the submarine for intelligence purposes. As "K-129" had sunk in very deep water, at a depth of 16,500 feet (), a large ship was required for the recovery operation. Such a vessel would be detected easily by Soviet vessels, which might then interfere with the operation, so an elaborate cover story was developed. The CIA contacted Hughes, who agreed to help.
In 1974, the ship recovered a portion of "K-129", but as the section was being lifted to the surface, a mechanical failure in the grapple caused two-thirds of the recovered section to break off. This lost section is said to have held many of the most-sought items, including the code book and nuclear missiles. The recovered section held two nuclear-tipped torpedoes and some cryptographic machines, along with the bodies of six Soviet submariners, who were given a formal, filmed burial at sea.
The operation became public in February 1975 when the "Los Angeles Times" published a story about "Project Jennifer". Other news organizations, including "The New York Times," added details. The CIA declined to either confirm or deny the reports, a tactic that became known as the Glomar response and subsequently used to confront all manner of journalistic and public inquiry, including Freedom of Information Act requests. The actual name, Project Azorian, became public only in 2010.
The publication "Red Star Rogue" (2005) by Kenneth Sewell claims "Project Jennifer" recovered virtually all of "K-129" from the ocean floor. Sewell states, "[D]espite an elaborate cover-up and the eventual claim that Project Jennifer had been a failure, most of "K-129" and the remains of the crew were, in fact, raised from the bottom of the Pacific and brought into the "Glomar Explorer"". 
A subsequent movie and book by Michael White and Norman Polmar ("Project Azorian: The CIA and the Raising of the K-129") revealed testimony from on-site crewmen as well as B&W video of the actual recovery operation. These sources indicate that only the forward of the submarine were recovered.
After Project Azorian.
Mothballing.
While the ship had an enormous lifting capacity, there was little interest in operating the vessel because of her great cost. From March to June 1976, the General Services Administration (GSA) published advertisements inviting businesses to submit proposals for leasing the ship. By the end of four months, GSA had received a total of seven bids, including a US$2 offer submitted by, Braden Ryan, a Lincoln, Nebraska college student, and a US$1.98 million offer ($ million in ) from a man who said he planned to seek a government contract to salvage the nuclear reactors of two United States submarines. The Lockheed Missile and Space Company submitted a US$3 million ($ million in ), two-year lease proposal contingent upon the company's ability to secure financing. GSA had already extended the bid deadline twice to allow Lockheed to find financial backers for its project without success and the agency concluded there was no reason to believe this would change during the near future.
Although the scientific community rallied to the defense of "Hughes Glomar Explorer", urging the president to maintain the ship as a national asset, no agency or department of the government wanted to assume the maintenance and operating cost. Subsequently, during September 1976, the GSA transferred "Hughes Glomar Explorer" to the Navy for storage, and during January 1977, after it was prepared for dry docking at a cost of more than two million dollars, the ship became part of the Navy's Suisun Bay Reserve Fleet.
Lease, sale and disposal.
In September 1978, Ocean Minerals Company consortium of Mountain View, California, announced it had leased "Hughes Glomar Explorer" and that in November would begin testing a prototype deepsea mining system in the Pacific Ocean. The consortium included subsidiaries of the Standard Oil Company of Indiana, Royal Dutch Shell, and Boskalis Westminster Group NV of the Netherlands. The consortium's prime contractor was the Lockheed Missiles and Space Company.
In 1997, the ship was moved to Atlantic Marine's shipyard in Mobile, Alabama, for conversion to a dynamically-positioned deep sea drilling ship, capable of drilling in waters of and, with some modification, up to , which is deeper than any other existing rig. The conversion cost more than $180 million ($ million in ) and was completed during the first quarter of 1998.
The conversion of the vessel from 1996-1998 was the start of a 30-year lease from the U.S. Navy to Global Marine Drilling at a cost of US$1 million per year ($ million per year in ). Global Marine merged with Santa Fe International Corporation during 2001 to become GlobalSantaFe Corporation, which merged with Transocean in November 2007 and operated the vessel as "GSF Explorer".
In 2010, Transocean acquired the vessel in return for a ($ million in ) cash payment.
The vessel was reflagged from Houston to Port Vila, Vanuatu, in the third quarter of 2013.
Transocean announced in April 2015 that the ship would be scrapped. The ship arrived at the ship breakers at Zhoushan, China, on June 5, 2015.