The logic of sedation was this: a conscious, frightened child in a flooded cave passage, unable to see, unable to move freely, being pulled through water by a stranger — any sudden movement could have fatal consequences. The passages in some sections were tight enough that a person who panicked and attempted to surface would have no surface to reach. A child who grabbed at a wall or a diver in a moment of panic could compromise the diver’s ability to control the buoyancy and direction of both. The passages were real: experienced divers had found them challenging. A child in distress, without training, would face compounded hazards.
Harris and the medical team developed a protocol using what were described in public reports as sedative agents — medications that would induce a state of reduced consciousness sufficient to prevent panic without suppressing respiration. The specific agents used were described in subsequent media reports, but the protocol’s key feature was that each boy would need re-dosing during the approximately three-hour transit from Nern Nom Sao to the surface, since no single dose could safely last the entire journey. Harris taught the other cave divers — people with no medical training beyond first aid — to recognize when a dose was wearing off and to administer the next dose at the appropriate moment.
The risks were acknowledged directly by those involved. Harris later described the medications as “essentially life-threatening anaesthetic drugs.” The dosing was calibrated to sedate without killing, but that calibration had been worked out without the ability to monitor the boys’ vitals in real time during the dive. Each boy was fitted with a full-face diving mask that supplied oxygen and covered the mouth and nose, reducing the risk of water inhalation if consciousness fluctuated, and was placed in a wetsuit for thermal protection in water that was significantly colder than the air temperature outside.