In 1960, the globe was gripped by space fever, and would-be astronauts fantasized about their first trips into space.

Captain Don Walsh, 28, on the other hand, had his eyes set on the ground. He was about to go deeper than any human had gone before.

The US Navy had acquired a bathyscaphe Trieste submersible, and Don, a submarine lieutenant, volunteered to join the research.

But when he joined up for the expedition, the deepest he’d ever been in a submarine was only 100 meters. He was in for a surprise when he learned that the US Navy wanted him to dive more than a hundred times deeper.

The objective was to travel to the lowest point on the earth, the Mariana Trench, a tiny undersea canyon in the Pacific Ocean off the coast of Guam.