Divers who take part in advanced diving activities must have a solid understanding of the physics and physiology associated with deeper dives. They also need to understand how their equipment functions and the limitations of both their equipment and their skills. Take the case of Kendall.
Kendall was a dive instructor working in a popular tropical destination. He was in good health, in his early 20s, and experienced in most aspects of recreational diving. He was assigned as the divemaster for a group of technical divers exploring a wreck with a maximum depth of 200 feet and no permanent mooring. Kendall descended to 108 feet, where he tied the boat into the wreck's mast. After the day's diving, the crew decided to attach a flotation ball on the anchor line and leave it in place for the next day.
Arriving on site the following day, the crew realized that the anchor line had fallen to the deck of the wreck. Kendall entered the water intending to bring the line back to the surface, a dive that would take about five minutes.
Ten minutes after Kendall descended, concerns about his safety prompted one of the technical divers to enter the water to find him. Following a bubble trail, the tech diver found Kendall drifting a good distance from the wreck at 100 feet. He was obviously dazed and had less than 500 psi remaining in his single cylinder.
Based on the limited remaining air supply, the short duration of the dive and Kendall's obvious mental confusion, the tech diver decided to bring Kendall directly to the surface in a controlled ascent.
Kendall was brought on board, assisted out of his gear and laid on his back. His computer indicated he had reached a maximum depth of 148 feet and that he had omitted a short required decompression stop at 10 feet.
Several minutes after surfacing, Kendall began to complain of some numbness in his left leg, a sign of possible decompression sickness. After a field neurological exam, he was placed on oxygen and transported immediately to the local recompression chamber. Treatment resolved all symptoms with no apparent complications.
Upon descending to 108 feet, Kendall found that the anchor line was entangled in the wreck at around 150 feet. Kendall had no training for making a dive to this depth, but he descended to free the line. Unfortunately, the work of pulling the heavy line free in the moderate current worsened his already increasing narcosis. Kendall ascended a few feet, hoping to clear the narcosis, but his confusion remained.
Upon checking his dive computer, he was surprised to find that he was now in a required-decompression situation. The computer was not designed for advanced decompression diving, and Kendall had never fully familiarized himself with the emergency deco function.
The most prominent command on the screen was "stop." So, Kendall stopped and drifted helplessly in the ocean at around 100 feet. Because of his lack of familiarity with the computer, he didn't realize that the deco stop was supposed to occur at 10 feet. By staying at 100 feet, Kendall was increasing his decompression obligation, not reducing it.
Lessons for Life
- Most dive computers will provide emergency decompression information. Unfortunately, many divers fail to familiarize themselves with these features or the skills for making emergency stops.
- Narcosis does not necessarily disappear immediately upon ascending a few feet. At the onset of obvious impairment, ascend until mental confusion clears or until you reach the surface.
- Kendall's dive plan was for a descent to 108 feet. When it became obvious that he could not accomplish the objective without descending much deeper, he should have ended the dive.
- The most important lesson here is that diving beyond the limits of your current training and experience requires more advanced training, including supervised dives.