Below more than a mile (1.6 kilometers) of ocean and three more (4.8 kilometers) of mud and rock, the prize is waiting. At the surface a massive drilling vessel called the Discoverer Enterprise strains to reach it. It's the spring of 2003, and for more than two months now the Enterprise has been holding steady over a spot 120 miles (190 kilometers) southeast of New Orleans in the Gulf of Mexico. The ship is driving a well toward an estimated one billion barrels of oil below the seafloor—the biggest oil field discovered in United States territory in three decades.

The 835-foot (255-meter) Enterprise shudders every few minutes as its thrusters put out a burst of power to fight the strong current.