Explorer: The Deepest Cave

A team of elite cavers led by 68-year-old Bill Stone attempts a months-long expedition to officially make Cheve Cave in Oaxaca, Mexico the world’s deepest cave. A massive logistical undertaking above ground supports the lead team in the depths as they navigate an underground maze of twisting tunnels and dead ends in search of a passage that leads to the bottom of deepest cave on earth. (National Geographic)