The divers aboard the "Southern Hercules" barge are 120 miles out to sea to disassemble and plug an aging subsea oil well. After detonating an explosive charge to cut the well pipes below the seafloor, they find that mysterious and potentially extremely dangerous bubbles are flowing from the well. Aboard the "Arapaho" heavy lift barge, the dive team faces a tight schedule and the constant threat of heavy weather as they take apart a massive platform by burning through steel underwater.