Heavy Lift Ship - Submerging Types

Submerging Types

Semi-submerging are more commonly known as a "flo/flo" for float-on/float-off. These vessels have a long and low well deck between a forward pilot house and an aft machinery space. In superficial appearance, it is somewhat similar to a dry bulk carrier or some forms of oil tanker. Its ballast tanks can be flooded to lower the well deck below the water's surface, allowing oil platforms, other vessels, or other floating cargo to be moved into position for loading. The tanks are then pumped out, and the well deck rises to shoulder the load. To balance the cargo, the various tanks can be pumped unevenly.

The flo/flo industry's largest customer base is the oil industry. They have transported many oil drilling rigs (flo/flo ships can carry the rigs from their construction site to a drilling site at roughly three to four times the speed of a self-deploying rig). Rapid deployment of the rig to the drilling site can translate into major savings to the oil industry. They also transport other outsized cargo and yachts.

The U.S. Navy has used such ships to bring two damaged warships back to the United States for repair. The first was the guided missile frigate USS Samuel B. Roberts, which was nearly sunk by a naval mine in the central Persian Gulf on 14 April 1988. The frigate was towed to Dubai, then floated home to Newport, Rhode Island, aboard Mighty Servant 2.

Eleven years later, MV Blue Marlin transported the U.S. guided missile destroyer USS Cole from Aden, Yemen to Pascagoula, Mississippi, after the warship was damaged in a bombing attack on 12 October 2000.

The U.S. Navy has also chartered other heavy lift ships to carry smaller craft, usually mine-countermeasure craft, or other patrol craft. Since there are no US-flagged heavy lift/flo/flo ships, the U.S. Navy normally relies on its Military Sealift Command to charter them from the world commercial market.

In 2004, Blue Marlin carried the world's largest semi-submersible oil platform, BP's Thunder Horse PDQ, from the Daewoo Shipbuilding & Marine Engineering (DMSE) shipyard in South Korea to Kiewit Offshore Services in Ingleside, Texas.

Many of the larger ships of this class are owned by the company Dockwise, including Mighty Servant 1, MV Blue Marlin, and MV Black Marlin. In 2004, Dockwise increased the deck width of Blue Marlin, to make it the then largest heavy transport carrier in the world until it was superseded by the launch of the Dockwise Vanguard in 2012. One of the company's vessels has been lost in recent years: Mighty Servant 2 which capsized after hitting an uncharted underwater obstacle off Indonesia in November 1999.