Cave Diving

What makes cave diving different

In open water, if something goes wrong, you can always swim up. In a cave there's solid rock above you, often for hundreds or thousands of metres of passage. You can only get out the way you came in, and you have to do it with the gas you carry. Visibility can drop from crystal clear to nothing in seconds if silt on the floor is disturbed. Diving in a place like this, called an overhead environment, needs different equipment, procedures and training.

Famous cave diving regions include the springs of north Florida in the United States and the cenotes of Mexico's Yucatán Peninsula, along with cave systems across Europe, Australia and the Caribbean.

Cavern and cave

Agencies separate two zones. Cavern diving stays within the area near the entrance where daylight is still visible, within limits on distance and depth set by training agencies. Cave diving goes beyond the reach of daylight into the cave proper. Even cavern diving needs a cavern course; cave diving needs further courses, built up in stages.

Lessons from accidents

Studies of cave diving deaths, beginning with work led by cave diving pioneer Sheck Exley in the 1970s, found that most victims broke one or more simple rules. Those rules are now the foundation of cave training:

• Get trained. Many cave diving deaths involve open-water divers with no cave training.
• Run a continuous guideline from open water, so you can find your way out even in zero visibility.
• Manage your gas with the rule of thirds.
• Stay within safe depth limits for your gas.
• Carry at least three lights.

The rule of thirds

Cave divers divide their gas supply into thirds: one third to swim in, one third to swim out and one third as a reserve for an emergency, such as sharing gas with a buddy all the way out. The dive is turned as soon as either diver has used a third of their gas. Many divers are even more conservative in caves with currents or long exits. How much gas you have to start with is explained in scuba tanks.

Equipment

Cave divers usually carry redundant gas supplies, often two tanks worn on the back or at the sides, each with its own regulator. They carry a primary light and at least two backups, line reels and markers, and cutting tools. Deep caves may need trimix to control narcosis. Perfect neutral buoyancy, horizontal trim and careful finning are essential to keep silt down.

Training

Cave training usually runs in steps: a cavern course, an introductory cave course and then a full cave course, sometimes followed by further specialties. Each adds skills such as line laying, lost-line and lost-buddy drills, gas sharing in zero visibility and complex navigation.

Frequently asked questions