The Deepwater Horizon was a 9-year-old[30] semi-submersible, mobile, floating, dynamically positioned drilling rig that could operate in waters up to 10,000 ft (3,000 m) deep.[31] Built by South Korean company Hyundai Heavy Industries[32] and owned by Transocean, the rig operated under the Marshallese flag of convenience, and was chartered to BP from March 2008 to September 2013.[2] It was drilling a deep exploratory well, 18,360 ft (5,600 m) below sea level, in approximately 5,100 ft (1,600 m) of water. The well is situated in the Macondo Prospect in Mississippi Canyon Block 252 (MC252) of the Gulf of Mexico, in the United States' exclusive economic zone. The Macondo well is found roughly 41 mi (66 km) off the Louisiana coast.[33][34] BP was the operator and principal developer of the Macondo Prospect with a 65% share, while 25% was owned by Anadarko Petroleum, and 10% by MOEX Offshore 2007, a unit of Mitsui.[35]