As explosion burst and oil leaked into the ocean. Billions of dollars rushed to the surface and water seemed to be on fire, but only oil burned. The uncontrollable fire burned up the derrick of Deepwater Horizon ,48 miles off the coast of Louisiana. British Productions (BP) leased Deepwater Horizon from Transocean, an oil rig company, which had the largest oil spill in U.S. history. The blowout, a large release of crude oil from the formation of oil, is more devastating offshore. It is more dangerous because you cannot run to safety. The water pushes harder on the already compressed formation so even more oil is released. BP’s blowout had a large political, environmental, and economical effect.Offshore oil rigs have many parts the run it. Deepwater Horizon had a derrick used to insert piping into the hole using the catwalk. It was a semi submersible and was not connected to the ocean floor, so it had a propulsion operating system for it to stay in place and to keep the pipe from bending. Deepwater Horizon was a MODU designed with a platform-type deck that contains drilling equipment and other machinery supported by pontoon-type columns. Deepwater Horizon was a fifth-generation, RBS-8D design , deepwater, dynamically positioned, column-stabilized,semi-submersible mobile offshore drilling unit, designed to drill subsea wells for oil exploration and production using a blowout preventer, and a 21 in outside diameter marine riser. During the final phases of drilling the exploratory well at Macondo, a geyser of seawater erupted from the marine reservoir on the rig, shooting 240 ft into the air. This was soon followed by the eruption of drilling mud, methane gas, and water. The gas component of quickly transitioned into a gaseous state and then was lighted by motors into a series of explosions and then a fiery mess. An attempt was made to activate the blowout preventer, but it failed. The final defense to prevent an oil spill, a device known as a blind shear ram, was activated but failed to plug the well because they hit a tool joint that was bent out of there reach due to the failure of the positioning system. At the time of the explosion, there were 126 crew on board; seven were employees of BP, 79 of Transocean, including Anadarko, Halliburton and M-I SWACO. Eleven workers were presumed killed in the initial explosion. The rig was evacuated, with injured workers airlifted to medical facilities. Deepwater Horizon sank on 22 April 2010. The remains of the rig were located resting on the seafloor.The oil spill continued until 15 July when it was closed by a cap.Relief wells were used to permanently seal the well.