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January 19, 2007
Caves and caverns
The first certification all of us earn is that of an "open water" diver. Open water? As opposed to what? Closed water? No, the "open" refers to the fact that you can go up and stick your head out of the water anytime. That's open water. Anything that's not "open water" is considered an "overhead environment." Examples of overhead environments are caves, caverns, going inside a wreck or diving under ice. When you dive in overhead environments you can't just go up if you're short on air. You first must find an exit. The implications of that are significant. And that is why diving in overhead environments requires additional training and certification.
This inevitably brings up questions. Diving in and by itself is wonderful. Breathing underwater, seeing all those sights, floating weightlessly. And the oceans are endless; it's not like you run out of things to see and experience. Why would anyone want to add to the risk by entering overhead environments that make everything more complicated and more dangerous?
Maybe it's just because the challenge is there, and people forever push the limits. Of all the dive books I've read so far, the majority deal with wreck diving and cave diving. The rest are generally introductions to scuba or textbooks on certain technical aspects, like specialized gear or diving physics. Caves and wrecks seems to be what fascinates a lot of divers, and some of the world's most famous dive sites are either wrecks or caves. Why?
I will always remember the night of my first dive in the pool, the first time I breathed underwater and we then went to the deep end of the pool. Apart from the sheer magnitude and thrill of the moment, the realization that I had done it and was breathing underwater, the one thing I remember most was how disoriented I felt. The world was essentially reduced to looking down or straight ahead and I never really knew where I was, even in the pool. At the time I attributed that to the newness of it all, and perhaps also to my black-skirted mask that did not allow glancing down or to the side. There's much discussion going on over what sort of mask is best, one that concentrates vision ahead or one that lets in as much light and vision as possible, but that's another topic. Fact is that orientation underwater, knowing where one is at all times, isn't easy, or at least it didn't come easy to me.
Even later, diving at Devil's Den in Florida, I didn't really know where I was most of the time. I know that because Carol asked me and I didn't know. And Devil's Den is a fairly confined environment. You swim around the big debris cone in the center and you can see the surface at all time. Devil's Den, of course, was new to me and when I dove there I still only had had a dozen dives or so to my name. But it also gave me my first glimpse of what an overhead environment might be like. Devil's Den isn't technically "overhead." Imagine a somewhat irregular sphere roughly halfway filled with water. There will be some places where the walls overhang. You look up and there is rock and you have to dive sideways and then up to the surface. That is still technically not even a cavern.
So what's a cavern and what's a cave? Definitions vary, but by and large a cavern is an underground area where you can still see the daylight within a certain distance and thus the exit. 
A cave is an overhead environment where you can't see daylight, or where daylight, and thus an exit, is so and so far away. The idea is that in caverns, you can always look around and see the exit. In caves you cannot see the exit and you must therefore know where you're going and what way is out. That is a huge difference. [The picture to the left is from the Tulum Cenote Dive Center in Mexico at cenotedive.com]
As a result, caverns and caves are treated very differently. Open water certified divers may dive in caverns, but only if accompanied by a cave-certified diver. Rules vary between agencies and locations, but all insist that anyone not trained in overhead environments have certified guidance. For cave diving, nothing other than true cave diving certification will do. There are also cavern diving courses and certifications, and they should be seen as sort of beginners classes towards "real" cave diving.
What makes cave diving so different? Different enough that rangers in certain dive sites that are mostly open water but do have caves (like the "Catfish sink" at Manatee Springs National Park in Florida) insist that you don't even take a dive light with you so as not to be tempted to go into the cave?
Well, I've never been in an underwater cave, but I've been in a few above ground. They are dark, and so you need a light. They can be narrow and constricting, and so you need to be comfortable in confined spaces. They are disorienting and you need to know the way out. And they tend to have offshoots that can easily turn them into maze-like labyrinths. Most people are somewhat intimidated by caves and some tend to panic. Now imagine being in a cave underwater where you have your dive gear on; where there are no lights on the ceiling of the cave and you need to bring your own; where there are currents and the possibility of poor visibility; and where you can run out of air. And where the cave may go deeper and you can't simply choose not to go that deep because that may be the only way through, or out. Wow.
As a result, cavern and cave training is very serious business. And the equipment used for cave diving is significantly more elaborate as well. Since you do need to see, you must bring a light along. But a light can fail. So you bring two, or better yet, three. Without air you're dead, and cave dives can be long and deep, so you bring along more air. Cave divers often use "doubles," dual tanks and a backup "pony" bottle to boot, and sometimes more. Since it is very easy to lose orientation, cave divers rely on lines. In well explored caves open as dive sites, there are permanent lines so that divers always know where to go, and which direction is out. But if a cave diver explores a new cave, running a new line and making sure it is tied off properly is a matter of life and death. And then there is the ever important visibility. Most caves have silt at the bottom, and fins can quickly stir that up to reduce visibility to almost zero. So if you lose your line and find yourself in a confined environment with zero visibility... you get the picture. What that means is that learning to fin without stirring up silt becomes a required skill.
If all this makes it sound like cave diving is dangerous, it is. A lot of people have died in caves, and not just new divers with inadequate training. So many divers died in Florida's caverns when they first became popular with sports divers in the 1970s or so that a lot of the caves were closed off and there was a real danger that all may be declared off-limits. The cave diving community realized that and, wisely, began developing procedures, training courses and materials, and required certification. Thanks to them, many of Florida's caves remain open, underground worlds that can apparently invoke thrills and bursts of adrenaline that I can only imagine at this point. Yet, even so, some caves are considered so dangerous that they were voluntarily blocked off. Even in Devil's Den I saw at least one grate that closed off an offshoot or cave entrance. Another is at the very popular Ginnie Springs.
Does that mean cave diving becomes completely safe once you have the proper training, certifications and equipment? The answer is no. It's dangerous. According to what I have read, the danger is highest to relatively inexperienced divers who go in and quickly panic. And to those who truly push the limits by exploring where no one has been before. One such maverick was Sheck Exley, the man who literally wrote the book on cave diving (several, actually). In 30 years he logged 4,000 cave dives. He was a meticulous, safety-conscious planner and perfectionist who continually and systematically advanced the state-of-the-art in a methodical -- not reckless -- manner. Yet, in the end his quest to go ever deeper cost him his life. In April of 1994, after having reached cave depths of a mind-boggling 881 feet on Trimix and other gasses, Exley went for a round number -- one thousand feet -- at Zacaton cave (a sinkhole, or "cenote," really) in Mexico. He did not come out alive (for details, click here).
What drives mankind to attempt such exploits? Is it a death wish, seeking thrills, an adrenaline rush, or pushing the state-of-the-art? What separates doable progress from reckless impossibilities? No one would, for example, shoot for being the first person to do a space walk without a suit. You can't. Diving a thousand feet deep into a cave seems almost as physically impossibly, yet somehow Exley concluded it was still within the limits of human endurance and possibility. It wasn't.
Maybe each of us has our own comfort level. Will I ever dive caves? I have no idea. Will I dive caverns? Most likely. The pictures I've seen look beautiful. Why do I even contemplate all this when I am still a total newcomer to the sport of scuba diving? Maybe for the same reason that drove me to write a detailed FAQ on superchargers for import cars before I had ever installed, tuned or even driven a supercharged vehicle -- and then have the audacity to publish it on an enthusiast website. I was ridiculed at first, but ended up its moderator and resident expert for a while. I love to learn about the more complex and extreme issues of everything I become involved in. I am a meticulate researcher and can quickly grasp concepts and sort of become an expert in any given field. I eventually did participate in the development of a supercharger for my vehicle, learned how to electronically tune it via a sophisticated computer-based engine tuning system, and then datalog everything at the racetrack. Learning theory first, then practice works for me.
I think back of being at the bottom of Catfish Sink at Manatee Springs State Park, near the entrance to the cave that connects the sink with the next open water basin about 500 feet downstream. Even just outside the siphon of the cave entry the walls were black. Carol and Ted had gone through there early on in their diving careers, just a year or two into it, duly certified for cave diving, of course. I asked her how it was inside, what one feels. She didn't tell me much. Maybe it's something one has to experience.
Posted by conradb212 at January 19, 2007 11:05 PM
