Katie Graham was trying to escape the cave she’d been trapped inside with her teammates for the past three days. She held her breath and cautiously swam underwater through the turbid flood that was all but completely filling an underground corridor, ominously dubbed Skeleton Canyon, in Sistema Huautla, the deepest cave in the Western Hemisphere.

Only a few inches of air existed between the water’s surface and the roof of the cave. When she emerged, she did so face first, her head tilted all the way back to put herself in the best breathing position.

With her nose and mouth pressed to the slimy limestone roof, she calmly inhaled and made a deliberate effort to move forward slowly so as not to