Cavern Diving

By Jeanne Bear Sleeper

Editors Note: This month's article discusses cavern diving only. Future issues will discuss cave diving.

What you call cavern diving depends upon where you dive. Most divers will agree that a cavern has an overhead obstruction that prevents a diver from going directly to the surface. If you dive in California, a cavern could be a 10 foot deep crevice in a rock ledge; in Hawaii, a short lava tube; in Florida, a big room at the start of a complex cave system; and in the Caribbean, a coral arch linking reef sections.

Cavern diving is defined by the Cave Diving Section of the National Speleological Society (NSS) as a dive with: 1) daylight visible from the entrance; 2) minimum visibility of 40 feet; 3) 70 foot maximum depth; 4) no restrictions that would prevent two divers from swimming through together; 5) no decompression; and 6) less than 130 linear feet from the surface.

The important point to understand is there are reasons for the regional differences. This makes it difficult to formulate one set of rules that apply sensibly to overhead obstructions everywhere. When you cavern dive, the rule of thumb is do it with proper training. There is no substitute for cavern training from a recognized cavern and cave diving instructor. Organizations that offer this training include the National Association for Cave Diving, the Cave Diving Section of the National Speleological Society, Inc., NASDS, NAUI, SSI and PADI.

General Guidelines

Cavern divers have restricted access to the surface and should stay in sight of sunlight. If you cannot see natural light, you have ceased being a cavern diver and started a cave dive, which has completely different requirements for equipment and training and is significantly more hazardous.

Cavern divers need to carry lights to enhance colors, highlight detail, see direction or signal. The most conservative school of thought says do not carry a light, so you will not be tempted to leave sight of sunlight. Another school of thought says only carry a single, small light for color enhancement, as you would on an open water dive. The be prepared for anything school says to carry a main light and a second as a backup.

Be forewarned that carrying lights has created too much of a temptation for some divers. Many have exceeded their original dive plan and training, using the light to turn a cavern dive into a cave dive and become fatality statistics. Of 446 fatality reports on file with NACD and NSS from 1960 through 1995, 159 involved accidents where there was a known dive plan. Forty percent of those 159 reports show a planned cavern dive that turned into a cave dive. The divers got into trouble and perished.

The question of lights is like politics;there are strong points with each argument and probably no single solution. The answer lies in the water, cavern shape and size, divers experience and ability to stick with the no cave dive plan. Being unable to see the proper direction to swim can be frightening. The anxiety and/or panic that follows can result in loss of problem solving ability and accidents. Carrying a sturdy, reliable light might seem like an easy ounce of prevention but the Florida cave diving accident records say it has contributed to untrained cavern diver deaths.

Cavern diving equipment is your normal open water gear;mask, fins, tank, regulator with submersible pressure gauge and two second stages, wetsuit, tables/computer, watch, depth gauge, slate and pencil, BC, weightbelt, knife, light(s), plus a reel and line in appropriate conditions. Notice that a snorkel is not on the list. It is of no use in a cavern and is one more thing to get entangled or bump the cave ceiling.

Many cavern divers use the one-third rule for planning air consumption. This means using one-third of your air going in, one-third coming out and keeping one-third as backup in case of emergency. The alternate rule of thumb is called the 1,200 psi rule;meaning you should end a dive with 1,200 psi in the tank. These are sound dive planning rules on any scuba dive.

Buoyancy control and a different style of kicking are the keys to not stirring up the silt in a cavern. Silt can be on the ceiling, walls and floor of a cavern. Touching the surface or kicking so water movement disturbs the sediment can cause silt clouds that reduce visibility to zero. Fine tune your buoyancy to neutral, bend your knees and barely fin from your ankles. Tiny ankle kicks will propel you through areas with powder fine silt on the bottom. If the bottom is a little more stable and the ceiling is not a concern, you can leave your legs in the bent position. However, instead of pushing down for the power portion of a kick, make the upstroke the power stroke and the downstroke a gentle movement.

Some caverns that are the big rooms at the start of a cave system have permanent lines anchored or tied to the walls. Never cut, untie or re-route these lines. You may see triangular markers on the lines. These are direction arrows and must not be removed or changed. Divers entering the area before you have placed the markers and expect them to be in the same place when they exit.

The last but perhaps the most important equipment you need is a safety attitude. Never permit overconfidence to allow you to rationalize violating recommended safety procedures. If you are trained and equipped only as a beginning cavern diver, that means you are NOT a cave diver. You do not have the skills required to penetrate a cave, no matter how tempting it is to peek a little farther.

Training Referral

Professional diving retailers and instructors can direct you to a cavern/cave diving instructor in your area. If you have an interest in using cavern diving as a stepping stone to cave diving, consider taking a weekend course sanctioned by the Cave Diving Section of the National Speleological Society, Inc., P.O. Box 950, Branford, FL 32008-0950 or the National Association for Cave Diving (NACD), P.O. Box 14492, Gainesville, FL 32604. You can also contact NASDS at (800) 735-3483; NAUI at (909) 621-5801; PADI at (800) 729-7234; or SSI at (970) 482-0883.


Cavern diving is a chance to look in new nooks and crannies for interesting plant or animal life and the beauty of underwater geological formations. Any time you dive in an area where your direct and immediate access to the surface is blocked, special training and equipment are necessary.

The Florida scuba community is acutely sensitive to the issue of untrained or inadequately trained scuba divers having accidents in their fabulous network of springs, caverns and caves. In their crystal clear, warm water springs, untrained divers have begun open water dives and ended up cave diving fatalities.

The local rules that make complete sense for Florida-style cavern dives may be overly restrictive for other waters. Until you are cavern trained and experienced, take a conservative, safety first approach.

Next months article will feature more detailed information on cave diving equipment, techniques and training. Maybe a Florida warm weather break and a cave diving class is what you need this winter!

Acknowledgment: Special thanks to Jeffrey Bozanic, NACD and NSS cave diving instructor, for his valuable research and input.