Mark struggled upward kicking hard — his only goal to reach the warm tropical sunshine far above. His mind flashed to the simplicity of the plan. What had gone wrong? Through blurred vision, he glanced at his gauges, seeing his computer's depth readout flash through 300 feet and his SPG needle fall into the red zone below 500 psi. If he could just reach the wall, maybe he could stop his descent. That was his final thought as he inhaled against a dead regulator and darkness closed in.
Mark and Will were both in their early twenties. Self-confessed adrenaline junkies known for pushing the limits of adventure sports, they had recently been certified as Advanced Open Water divers. Mark and Will were eager to try deep diving, but before seeking training, they set off on a weeklong dive trip to the tropics.
Over margaritas one night, Mark listened to a team of tech divers discussing their dive to a wreck hanging on the edge of a deep wall at 200 feet. Mark immediately decided if those guys could do it, so could he. At the bar, he sketched out a plan to do a quick bounce dive on the wreck the following day. After a little arm-twisting, Will agreed to join Mark in his plan.
They quickly discovered that none of the island's responsible dive operators would take them out on such a foolish stunt. Undeterred, the divers rented a boat and hired Bill and Sarah, vacationing college students who agreed to skipper the boat.
At the approximate location of the wreck, the boat's depth finder confirmed the edge of the wall and a depth of thousands of feet on the seaward side. Mark and Will suited up in tropical BCs, rental regulators and single aluminum 80-cubic-foot tanks. The divers quickly reviewed their dive plan.
Mark figured the wreck would be easy to locate. In order to get down quickly, they would dump all of the air out of their BCs and wear extra weight. The pair would stop their descent with their power inflators. It would be a quick bounce dive. If either diver reached 1,500 psi or the bottom time exceeded six minutes, they would ascend immediately.
Mark and Will stepped off the swim platform and immediately began their descent. Dropping rapidly, the divers swam to within an arm's reach of the wall, scanning for the wreck and letting negative buoyancy carry them deeper.
Though he was descending more slowly than Mark, Will's dive computer couldn't keep up with the descent. Later, Will recalled that at 150 feet, he felt "short of breath" and "disconnected from my body."
The rapid descent had brought on a serious bout of nitrogen narcosis. His body was unable to acclimate to the increasing pressure and the growing load of nitrogen and carbon dioxide in his tissues. Making matters worse, his rental regulator was not designed for extreme depths and was struggling to deliver sufficient air. Will was bordering on panic. He was "overbreathing" his regulator, demanding more air, and at a faster rate, than it was capable of providing.
Scared and confused, Will reached out to grab a passing coral head, cutting his hand but stopping his descent at 156 feet. He turned to signal Mark to abort the dive, only to find his buddy much deeper, still rapidly descending.
Will faced several moments of indecision, complicated by narcosis. Before he could do anything to save himself or Mark, he needed to establish neutral buoyancy. Will fumbled for the inflator button on his BC and squeezed hard.
Meanwhile, Mark sailed downward, searching for the outline of the wreck. He was soon past 200 feet, and the wreck was nowhere in sight. Realizing the dive was rapidly spinning out of control, he reached for his power inflator, but at his depth and rate of descent it was a losing battle. Mark's BC now required seven times as much air to inflate as it would on the surface, and the inflator simply couldn't keep pace with his rapid descent.
Panicked, Mark began to kick hard toward the surface, but strenuous exertion only added to the debilitating effects of narcosis and carbon dioxide buildup. It's likely that Mark suffered deepwater blackout and drowned.
Having arrested his descent by clinging to the wall, Will was able to inflate his BC. As he rapidly ascended, the fog of narcosis began to lift, and Will regained the presence of mind to slow his ascent at around 70 feet. He had enough air to complete a short safety stop at 15 feet, but surfaced with his computer showing a decompression violation.
In spite of his rapid ascent and omitted decompression, Will was lucky. He suffered no notable symptoms of decompression sickness. Mark's body was never found.
Lessons for Life
Deep diving requires proper training, planning, topside support and gear. Divers need a larger gas supply, high-performance regulators and high-capacity BCs.
Extra Weight is dangerous on a deep dive. The compression of wetsuits and BCs compounds negative buoyancy. At about 200 feet, negative buoyancy is self-propagating.
Rapid Descents aggravate nitrogen narcosis. The maximum safe descent rate is 70 feet per minute. Pauses allow the body to compensate for the increasing pressure.