If it rains, the water can come up to the roof of the cave you’re in and flood segments of the tunnel. You have to know which sections might flood and always have a bailout plan. When the water comes up, you’ve got two choices: sit down and wait until it recedes or use diving gear to get out. Some of my colleagues in Papua New Guinea once had to bolt themselves 90 feet up on the side of a canyon while the water rose to within a few feet of them. All three hung on that top bolt for close to 18 hours before the water went down enough for them to get out.
Stone has explored some of the world’s deepest caves, including Mexico’s 4,869-foot Sistema Cheve.