Plunging into the deep, dark abyss of the Pacific Ocean’s Mariana Trench, U.S. Navy Lt. Don Walsh and Swiss engineer Jacques Piccard heard a loud cracking sound in their vessel—the bathyscaphe Trieste, which the Office of Naval Research (ONR) purchased for scientific observations. Already 30,000 ft. below sea level, Walsh and Piccard faced the ultimate decision—risk their lives to become