Explorer Robbie Schmitter prowls an underwater cave.
Image courtesy of Gavin Newman, top left image courtesy of Radek Husak
It was the wrong day for Stephen Bogaerts to have forgotten his wet suit, but forget it he had. What followed this realization was a manic drive back to the diving center, then a hurried leap into the water. The hour-long delay turned out to be fortuitous. His diving partner, Robbie Schmittner, was swimming downstream from a different starting point, carried by a current that Bogaerts would be fighting on his opposite path. Normally the current rages, but on the day in question, January 23, 2007, it was unusually gentle. So Bogaerts reached the rendezvous point a half hour sooner than expected, and Schmittner 20 minutes later. As Schmittner turned the last corner, he saw Bogaerts’s light flickering in the distance. The ethereal glow marked the juncture of two giant caves—Sac Actun and Nohoch Nah Chich. With their discovery of the opening, the divers had proved that the two caves were really one, now called simply Sac Actun. At the time, that made it the largest known underwater cave in the world, with almost a hundred miles of passages charted. Schmittner dropped a bottle of Moët & Chandon champagne to the cave floor to mark their arrival at that special juncture in one of the world’s greatest (yet least heralded) natural wonders.
For Schmittner and Bogaerts, the exploration is never done. After they discovered the Sac Actun connection in 2007, another Yucatán team showed that the underwater cave Ox Bel Ha, at 170 kilometers (106 miles), was longer still. But the race for the longest is not over. Recently Schmittner and Bogaerts were excited to learn that Sac Actun lies within 18 feet of Dos Ojos, another cave system. If they find a connection between the two, the union could again put Sac Actun on top and possibly make it the world’s second-longest cave, underwater or otherwise, depending on how long the connecting passage is. The pair hope to then find a link with Ox Bel Ha. If all those caves are joined, the whole system would rank behind only Mammoth Cave in Kentucky, which has almost 600 kilometers (about 370 miles) of passageways. At the pace Schmittner and Bogaerts are going, even overtaking Mammoth Cave—thought by many in the caving community to be a ridiculous goal—might be a possibility.
The two explorers, both diving instructors, have spent nearly a decade charting the Yucatán’s vast network of underwater caves, which they enter through portals called cenotes—sinkholes in the limestone that forms the peninsula south of Cancún. In some of the cenotes, the water is so clear that when you look up from the bottom, fish seem to be swimming in the sky. Clear or not, when you reach the bottom of a cenote you find tunnels, often marked by stalactites, stretching out under the earth. Go one way and you encounter caverns so vast that a 747 could fly through; Bogaerts and Schmittner navigate these with torpedo-shaped scooters. Go another way and you might run into passages so narrow that navigating them becomes a process of spelunking more than swimming. As you take in the grandeur—or snake your way through—only the sound of your breathing reminds you that you are out of your element.
