The Cenote

Yaretzi had been guiding divers through the cenotes of Yucatán for eleven years. That morning, before a forty-minute dive, she gave her usual briefing to Rasmus, a Danish diver with plenty of open-water experience but only a few cave dives behind him. "The white line is your lifeline," she told him, tapping the thin nylon cord that ran from the entrance into the dark. "The little plastic arrows on it always point toward the way out. And keep your fins away from the floor. That silt is as fine as flour."

For twenty minutes, they glided slowly through rooms full of stalactites that had formed thousands of years earlier, when the cave was still dry, and their lights turned the water a pale, impossible blue. At the agreed point, having used a third of their air, Yaretzi signalled that it was time to turn back. It was a rule she never broke: a third to go in, a third to come out, and a third in case something went wrong.

Something did. On the way back, the passage narrowed, and Rasmus, who had been swimming a little too low for several minutes, kicked hard to get round a rock. Around them, a brown cloud rose silently from the floor and swallowed everything. Within seconds Yaretzi couldn't see her own hand, let alone the line. Her light, instead of helping, simply lit up the silt in front of her mask, so that she seemed to be swimming inside a cup of coffee.

Fortunately, her left hand was already on the line. She had trained for exactly this moment so often that her fingers moved before her mind did: she made a ring with her thumb and finger around the cord, so it couldn't slip away. She felt Rasmus grab her ankle, and she reached back and squeezed his hand twice to tell him that she was there. Then she did the only thing that made sense in a world without light. She closed her eyes.

With her eyes shut, the cave became a place of touch. She moved forward steadily, feeling the line run through her fingers. At one point the line was wrapped around a rock, and she had to open her fingers for a second to get past it. She closed them again on the other side and twisted around the rock. A moment later, something felt wrong, and she stopped. Carefully, she felt along the cord for one of the plastic arrows and traced its shape. It pointed back over her shoulder. Somewhere around that rock she had closed her fingers on the wrong side of the line, and since then she had been leading them deeper into the cave.

She turned, tugged the line once to steady herself, and started again. She counted her breaths instead of the minutes and refused to think about the air she was using. Gradually, the darkness behind her eyelids became less complete, as if someone were slowly turning up a light. When she finally opened her eyes, the silt was behind them, and far ahead, at the end of the white cord, there was a faint green glow. It was sunlight falling through the entrance of the cenote, exactly where the arrows had promised it would be.