The dark and forbidding depths of the Gulf of Mexico, once frequented by only the hardiest of sea creatures, are now alive with human activity. Miniature submarines and robot-like vehicles prowl the ocean bottom while divers wend their way around incredible underwater structures -- taller than Manhattan skyscrapers but almost totally beneath the surface of the waves. This is the new geological frontier, and a daring breed of modern-day explorers is using technology worthy of Jules Verne and Jacques Cousteau to find fresh supplies of oil and natural gas.
Until recently, drilling in the Gulf was concentrated close to shore in...