Sink a big pipe, crank a pump, and - voilà! - you've entered a world powered by ocean water. Once primed, the pipe acts like a giant siphon, requiring relatively little energy to keep an inexhaustible supply of cold at hand. Already, 39-degree-Fahrenheit water courses through the Natural Energy Lab's newest pipe - a 55-inch-diameter, 9,000-foot-long polyethylene behemoth - at the rate of 27,000 gallons a minute, 24 hours a day.