The cave is still there. The mountain is still there. The bronze statue of Saman Kunan stands at the entrance. And the thirteen people who were found alive on a mud shelf four kilometers inside a flooded mountain on July 2, 2018, are still alive in the world.
## The Cave Diving Discipline: What It Actually Requires
To understand what the rescue divers accomplished at Tham Luang, it helps to understand what cave diving is and why it is considered among the most hazardous activities practiced by human beings.
Standard recreational scuba diving takes place in open water — the ocean, a lake, a reservoir — where the diver can at any point ascend directly to the surface if something goes wrong. The ocean surface is always there, always accessible, always a few meters away. This accessibility is the fundamental safety feature that makes recreational diving manageable for millions of people worldwide.
Cave diving removes that feature entirely. A cave diver in a flooded passage is separated from open air by the rock above and around them and by the water ahead and behind. There is no ascent route. The only exit is the way in, following the guideline back through whatever length of flooded passage lies between the diver and the air outside. If the guideline is lost, navigation becomes impossible in zero-visibility water where every tunnel looks identical by touch. If the breathing supply is exhausted before the exit is reached, there is no option available.
The community that practices cave diving has developed a set of principles intended to minimize the death rate in this inherently high-risk activity. The most fundamental is the rule of thirds: one third of the breathing gas supply is used for the inward journey, one third for the return, and one third is held in reserve for emergency. The emergency reserve exists because emergencies in caves consume gas faster than normal diving — the exertion of problem-solving, the currents that require more effort to swim against, the time spent helping a diver in difficulty.