On 20 April 2010, the largest accidental marine oil spill in the history of the petroleum industry took place in the Gulf of Mexico on the BP-operated Macondo Prospect. This blowout event on the Deepwater Horizon oil rig resulted with a total oil discharge of 4.9 million barrels, from the well that flowed for 87 days, until it was capped on 15 July 2010, after several failed attempts. The operation that finally capped the well successfully, was a joint effort of a few ROV teams, all working together at the same time. This disaster lead to many changes in the safety regulations within the oil and gas drilling industry. One of the most distinct regulation is that every oil rig operation must have an ROV with an intervention skid mounted on it, and by that the ROV could Independently shut down the well from the Blowout Preventer Unit (BOP) when all other safety system have failed.
Click on the image to see a video of the ROV operation that capped the Horizon well: