 |
According to the old saying, "Curiosity killed the cat." The same holds true for open-water divers who swim into flooded caverns and caves beyond the limits of their gear and abilities.
In the words of the National Association of Cave Diving (NACD): "Cave diving is deceptively easy." Of course, they mean it's a deceptively easy way for the untrained to die. The caverns and caves of central Florida alone have claimed well over 400 divers--yet thousands of tech divers safely visit these same passages every year. What's the difference between statistic and survivor? Proper training in cave diving techniques.
Silt Happens
The closed environment of flooded caves and caverns--the thing that makes them so interesting in the first place--also creates a world of unique hazards. Minimizing these hazards requires a different set of skills and techniques than those you learned in any open-water certification course.
Some hazards are obvious: low or zero light, the maze-like passageways that require penetration lines to follow, the inability to surface in case of emergencies. But one of the less obvious hazards of cave and cavern diving is silt. It's found in nearly every cave system. Whether composed of clay, decomposing vegetation or both, silt has the ability to eradicate visibility. One wrong fin kick or errant hand scull and the air-clear water becomes brown murk, and it can stay that way for days.
The solution to this hazard is spot-on buoyancy control and modified finning techniques that are at the heart of cavern and cave training.
Mastering Buoyancy Control
 |
Expert buoyancy control is largely a matter of weighting. Most recreational divers come to cavern classes overweighted. As a matter of practice, there has never been a reason for them to fine-tune their buoyancy, and most are surprised to find one of their first tasks is removing excess weight.
Overweighted divers have a tendency to swim through the water in a very inefficient position. The ballast weight pulls the diver's lower body down while the buoyancy in the BC pulls the shoulders up, giving the diver the hydrodynamics of a Peterbilt truck. This position also forces water from every kick of the fins directly into the silt on the bottom of the cavern.
In addition to losing some weight, divers typically have to relocate the weight on their gear to achieve proper trim in the water. Ideally, the cavern diver will swim through the water with a slightly head-down attitude. This places the fins slightly above the midline of the body and directs the thrust of the fins up and away from the sediments on the bottom of the cavern.
There are a number of methods for accomplishing this trim modification, including holders that position weights on the tank directly behind the shoulders. This brings the buoyancy of the BC in line with the ballast weight, helping to achieve neutral buoyancy without rotating the diver into an upright position.
Cave and cavern divers also trade aluminum tanks, which become positively buoyant at the end of the dive, for steel tanks, which maintain slightly negative buoyancy even when empty. The steel cylinder also provides a better distribution of negative buoyancy because of the weight-to-size ratio.
Another difference between open-water diving and cavern diving is that weights are positioned so that they cannot be dumped. In open water, dumping your weights assists you in reaching the surface. Inside a cave, the same act results in pinning you helplessly to the ceiling.
The whole process can be summed up as the rule of minimums: Use the minimum amount of weight required to achieve neutral buoyancy with the minimum amount of air in your BC.
|
|
|
Modified fin kicks are another adaptation divers must make when entering a cave environment. Cave and cavern divers rarely use the full flutter kick because it produces too much turbulence directed toward the bottom.
more...
|
The popularity of freshwater spring diving has led to some confusion among divers about cave and cavern environments and the limitations that apply.
more...
|
|
