The world’s largest hydrofoil wasn’t really a hydrofoil at all. In fact, it was one of a series of unique machines called "ground effect" vehicles built by the Soviet Union beginning in the 1960s.
The Soviets had a monopoly on this fascinating technology, relying on a little-known principle of physics - the "ground effect" - in which a dense cushion of air hugging the ground can provide more lift to a vehicle than air at higher altitudes.
Hovering about 3 - 12 feet above the ground, these vehicles resemble Luke Skywalker’s levitating craft from Star Wars, and far more fuel-efficient than airplanes, helicopters, hydrofoil, or cars. And at 58 feet, the largest of these, the "Caspian Sea Monster" was given its distinctive name after CIA analyst saw it at the Caspian port of Baku in photos taken by spy satellites. The craft traveled at speeds of up to 240 mph, had a swiveling nose cone for cargo loading, and could carry up to as many as 150 passengers.