There are three main classifications of diving: cave diving, open-water diving and cavern diving. Open-water diving is where all divers start gaining experience, and it’s defined as a dive in which linear access to the surface is directly available — in other words, by swimming straight up, a diver should be able to get a head above water, and sunlight is easily visible. In cavern diving, on the other hand, a diver is exploring permanent, naturally occurring caverns and has a ceiling overhead, but an entrance and visible light from the sun are in sight. Both open-water diving and cavern diving are considered recreational activities that require recreational-level certifications and training, and divers usually limit descents to 130 feet.
Cave diving differs from the other two types of diving in that it’s a form of technical diving instead of a recreational one. It requires a much different set of equipment and several years of training and certification, and professionals constantly stress the need for top-notch fitness and gear. But above all, they admire cave diving for its unique challenge and the potential to discover the undiscovered — scientific research gathered from cave dives can lead to the study of rare organisms and even offer cures to diseases like leukemia.
The best way to tell a cave diver apart from an open-water diver or cavern diver is to look at the equipment in use.
It’s important to remember that cave divers carry redundant equipment — this means that for every piece of equipment they carry, an extra will come along for the dive. This is to make sure that if something undergoes failure, there’s a replacement to take over and allow a safe return to the surface. It could be something seemingly unimportant like an extra mask, or a piece of equipment that ensures a diver’s survival, like an oxygen tank.
To understand the dangers of diving at high pressures underwater, it’s best to look at a soda bottle. When you shake a soda bottle, some bubbles go up to the surface. It doesn’t look like much at first, but if you quickly open up the cap, there’s a burst of fizzy gas as bubbles continue to climb up toward the surface.
There’s a way to keep this from happening and making a mess. If you’ve dropped a bottle of soda on the ground, you can prevent it from bubbling up and creating too much pressure by opening the cap very slowly. If the gas inside the bottle is gradually let out, a small amount of bubbles will form, and the pressure will be decreased.
Since cave diving is different from other recreational diving activities, many of the techniques people use are also much different. Divers are taught to swim in a prone, or face down, position, with the knees bent and the fins elevated above the plane of the body. This is mainly a precaution against kicking the bottom of a cave and stirring up sediment, but it also offers a good streamline and creates little resistance to the water.
Cave divers move about a cave by using a simple technique called “pull and glide” — using the tips of their fingers, divers look for crevices in rock for a place to hook onto. The rock is usually something hard and porous like limestone, so it should have lots of pockets and places to grab. After grabbing hold, divers pull and release, gliding through the cave with relative ease.
So how does someone become a cave diver? Can anyone do it, or does it require a great deal of training and expertise? Because cave diving is technical in nature, the activity isn’t something anyone can jump into and do well or safely.
You should have a minimum of 50 open-water dives before you even consider cavern or cave diving. From there, once you start cavern diving, you should have close to a week of actual class time.”
One of the most claustrophobic & terrifying movies of cave diving – Sanctum