When diving in a cavern you have to be aware of the limitations that you must follow religiously. The reason is that most accidents in caves or caverns occur because divers don’t follow these limitations. So if you plan to cavern please don’t deviate from these.
This is the first and most important limitation. When cavern diving you should always be able to see the exit, and that exit must be illuminated by daylight. Many things can stop you from seeing the daylight and thus stop you from penetrating further into the cavern. Open water divers, swimmers, the amount of recent rain fall even the time of day can all effect the reach of the daylight zone.
When diving in a cavern you are in an overhead environment. This means that we no longer have direct access to the surface and the abundant gas supply that is there. This means that you have to use the rule of thirds. One third of your gas supply to get where you are going, one third to get back, and one third for any emergencies. If you are not using a single cylinder but are using twins instead, you must only use one sixth of your available supply. This is to limit the distance that you penetrate and help keep you safe.
When diving in a cavern the NACD puts a linear penetration distance of 200ft from the surface. That means, if the cavern zone ends at a depth of 75ft then you must only penetrate a distance of 125ft. Also no dive should be deeper than 100ft.
At the start of a cavern dive there must be a minimum visibility of 30ft. This is determined by a diver being able to see and recognize a lighted hand signal. Visibility does not have to remain at 30ft for the whole dive but if it degrades to such a point where the visibility of the daylight zone is compromised then the dive should be ended.
No Decompression Diving
Exactly as it says. As a cavern diver you must not go into deco.
There are two types of restriction: minor restrictions and major restrictions. Minor restrictions are when two divers cannot swim side by side. Major restrictions are where you may have to actually remove or adjusted your equipment to pass through. Neither of these are allowed in cavern diving.
A three minute safety stop must always be performed at the end of the dive.
You must always have a continues guideline to open water. You may not need one to enter but you may need one to exit. Set the line as this is your life line to the exit and always know where it is. The primary tie-off must be placed in open water, the secondary tie-off must be placed at the start of the cavern zone.
Correctly Configured Equipment
It is possibles dive in the cavern zone with just regular recreational equipment. However, in addition to the recreational equipment you should have a minimum of two lights, a primary reel, two safety reels/spools, and two cutting devices, it is also recommended that you cylinder has two valves and that you use two first stages each with it’s own second stage. One of the second stages should have a long hose (7ft or 2m).
Regardless of all these limitations, you must be trained. Going into the cavern zone without the proper training can result in death. Make sure that you get trained by someone that is highly experienced and who cave and cavern dives regularly.