How a boat briefly reached 317 miles per hour
The record belongs to Spirit of Australia, a small hydroplane driven by Ken Warby. In 1978, on Australia’s Blowering Dam, it set the world water-speed record at 317.6 miles per hour (511.1 kilometers per hour). The mark still stands. The craft was not a conventional boat pushing its hull through the water; at record speed, only a small part of its structure touched the surface.
Why riding on top of the water reduces drag
The design is called a three-point hydroplane. Its hull has two contact points near the front and a small rear contact point. As speed builds, water pressure lifts most of the hull clear, leaving those points to support and steady the craft. Less hull rubbing against water means less drag—the force that resists motion.
That lift creates a delicate balance. The boat must skim high enough to avoid plowing through the water, but not so high that it loses stable contact and pitches out of control. Its shape, weight distribution, and steering all help keep it at the narrow operating angle where the hull can ride on a thin film of water.
The speed record is a stability problem, too
At hundreds of miles per hour, even a small change in wind, water surface, or steering can upset that balance. A hydroplane can begin to lift like an aircraft; if it rises too far, the airflow may flip it. The challenge is not simply supplying more engine power, but directing that power into a craft that stays controllable on an uneven surface.
Warby built Spirit of Australia largely himself, using a jet engine and a compact wooden hull. Its record endured not because later engineers stopped pursuing speed, but because breaking it requires a rare combination: enough thrust to go faster, and a design stable enough to survive the attempt. The boat’s astonishing speed came from minimizing contact with water—while never being able to eliminate that contact entirely.
