The Virgin Oceanic adventurers currently vying to reach the bottom of the Mariana Trench are following in the path of two trailblazers who took the plunge in a peculiar underwater vehicle 52 years ago. IEEE Spectrum recently interviewed Don Walsh, who was a U.S. Navy lieutenant and a submariner when he made the journey down with Swiss engineer Jacques Piccard in 1960. To date, those two men are the only human beings who have laid eyes on the Mariana Trench seafloor—and in an ironic twist, they didn’t see much of anything.

They made the trip in a vehicle called a bathyscaphe, which looked something like an underwater dirigible. The crew cabin, a cramped steel sphere, was suspended from a massive tank holding about 130 000 liters of gasoline—which, with less density than water, would provide the buoyancy necessary to lift the craft from the chasm. Piccard and his father designed the vehicle together and sold it to the U.S. Navy in 1958.

Continue reading this incredible story (with multiple sound clips from an interview) on ieee spectrum.