In the 1970s, the oil and natural gas industry decided to take a leap into the deep. With many of the biggest and cheapest petroleum deposits on land already discovered, the search for new finds went offshore into ever-deeper waters.

The move has transformed the energy business. About one-third of the world's oil and gas now comes from beneath the seabed, although some accidents and spills have caused extensive damage to the environment and been costly to clean up.

Despite the risks and technical challenges, the mining industry is about to do what oil and gas drillers have done. Buoyed by recent high prices of precious and base metals, leading mining and mineral-using economies are on the verge of opening a new frontier of deep-sea metals recovery.