Oil companies, navies and oceanographers are always trying to sharpen their picture of the ocean floor. Until now, they've relied largely on surveys performed by remotely operated vehicles, tethered by cables to ships. But the tethers restrict how deep and fast the unmanned vehicles can go. Now, thanks to advances in artificial intelligence, a few companies are building completely cable-free autonomous underwater vehicles that can gather data on explosive mines or new offshore oil-drilling sites faster and more cheaply than remotely operated vehicles.

Several large manufacturers, including Boeing, Lockheed Martin, Norway's Kongsberg Simrad and Denmark's Maridan make autonomous underwater vehicles. But despite the impressive competition, a startup based in Cambridge, MA, called Bluefin Robotics may be leading the pack. It has sold 16 robots to universities and the U.S. Department of Defense in the last three years and recently sold another to its first private-sector customer, an oil and gas survey company.

A three-meter-long Bluefin submarine is programmed with the latest in autonomous control systems. Bluefin engineers might define a square of ocean floor for the submarine to survey; low-level software would guide the craft back and forth across that area, directing it when to turn, while high-level safety and self-monitoring functions would enforce rules to protect the vehicle-for example, forbidding it to go within 10 meters of the ocean floor. The advantage is that Bluefin's customers can specify mission goals without having to anticipate every possible glitch, because the vehicle knows how to protect itself.

The Bluefin craft can't yet handle subtler tasks such as finding a pipeline and then following it. But given further advances in areas such as image recognition, says Roger Lott, head of surveying at BP, autonomous submarines have the potential to make underwater surveys "orders of magnitude" more efficient.