Sheck Exley wrote the book on cave diving. Literally.

Sheck Exley (1949-1994) doing what he loved

If the title of his book Basic Cave Diving: A Blueprint for Survival sounds dramatic, that’s because cave diving is dramatic. Imagine all the fun and danger of SCUBA diving, combined with all the fun and danger of cave exploration, except turned up to 11.

Irby Sheck Exley, Jr. (yes, that was his real name, on his birth certificate) was born in Jacksonville, Florida on April 1, 1949, son of a Volkswagen dealer. His younger brother drowned at age 17; perhaps that is what sparked his desire to make cave diving safer for others, but I don’t want to read too much into other people’s motivations. The important thing is that he did care deeply about making cave diving safe for others. 

The one thing you must understand about cave diving is that it is completely insane. SCUBA diving is dangerous in itself – carrying your own air into a place where you would normally die is an obvious danger, but even if you do everything right you could still die of nitrogen narcosis.

Cave diving adds a new set of dangers. Sunlight can pass through hundreds of feet of open water, but not through rock, so it’s DARK in there, bring your own light. Some passageways are no bigger than you are, so you can go in only to get stuck on the way out. Swimming can stir up mud and silt, reducing visibility to near zero. And with rock above, around, and below, it’s easy to lose sight of where you are and where you are going. There are hundreds of ways to die, and if science has taught us one thing, it’s that nature doesn’t care whether you live or die.

Even with all these dangers, thousands of people enjoy cave diving. I’m not one of them, and I have no interest in becoming one, but I can definitely see the appeal. I have a great admiration for people who push themselves to the absolute limit of human ability, even in the most unexpected ways. Especially in the most unexpected ways.

And for people who love cave diving, there is no better place in the world than Sheck Exley’s northern Florida. There are only a few places in the world with both the right rock type and the heavy rains required to create karst topography, home of the most elaborate cave systems – Slovenia, southern Thailand, Mexico’s Yucatán Peninsula – but northern Florida is unique even among these places because of its high water table. There are no above-ground cave systems like Postojna or Tham Luang there; all of Florida’s cave systems are underwater, with entrances at springs and sinkholes.

Even though I’ve never been cave diving – and the thought of it terrifies me – I have some experience with cave divers. Some of my favorite childhood memories are of camping at Florida’s Ginnie Springs,  one of the most famous cave diving destinations in Florida, and thus in the whole world. That means I almost certainly saw Sheck Exley before his death in 1994, although I didn’t know it at the time.

Exley took a job as a math teacher at Suwanee High School in Live Oak, Florida, so he could live close to his beloved springs. His list of SCUBA diving records, in both open water and cave diving, stretches farther than the deepest cave. He was the first person in the world to log 1,000 cave dives – all before he turned 24. He has had the deepest penetration of numerous caves in Florida and elsewhere. He was the first person in the world to dive to a depth of 800 feet (240 meters), a grueling dive that required more than 13 hours of gradual post-dive decompression. 

But without a doubt, his greatest contribution to the sport of cave diving was his obsession with doing it safely. His book is now required reading for many cave diving certifications – meaning that aspiring divers can’t legally enter their first cave until they know how to do it like Exley did. He also helped popularize the use of the “Octopus,” a secondary diving regulator so that your buddy can breathe from your tank if theirs runs out.

Unfortunately, even for a man who literally wrote the book on safe cave diving, cave diving is still a dangerous sport, and ultimately it took Sheck Exley. On August 6, 1994, Exley died in Mexico’s Zacatón Sinkhole while trying to become the first person to descend to 1,000 feet (300 meters) in freshwater. His cause of death is uncertain, but likely due to the effects of breathing a mix of helium gas under high pressure – effects which are poorly-understood even 24 years later, simply because so few people have ever tried.

But there is one detail of his death that is both fitting and heartbreaking. When he didn’t come up at the scheduled time, his friends in the surface support crew knew he was gone – but they never expected what they were about to see when they pulled up the air hose. With his literal dying breath, Exley had wrapped himself firmly in the air hose, saving his friends from a risky mission to recover his body. But that’s who he was: right up until the end, finding ways to keep everyone safe.

Sheck Exley may be dead, but there are literally hundreds of people alive today because of him.

Aloha `oe, Sheck.