Antonio lay helpless on the surface. He could see the boat moving closer to him, or at least he thought he could. Everything was a fog. His feet felt like useless blocks of lead dragging him back to the depths below. As he fought to keep his face above water, Antonio tried to recall what had happened. His concentration was fading, but he remembered being entangled at 170 feet; he recalled sharply the terror of running out of gas at 210 feet. Nothing else seemed to make sense, and now even his vision was gray. Why couldn't he see? What had happened to Juan? Everything was a blur as he heard the muffled shouts of the safety divers pulling him back to the boat.

The Divers

Antonio, an enthusiastic technical diver who had just completed trimix training, was buddied with Juan, a technical dive instructor with a great deal of experience. Both divers were in their early 40s and in reasonably good health.

The Dive

Juan and Antonio were diving an Atlantic shipwreck in 235 feet of seawater. They planned a 20-minute dive to the main deck at 210 feet using trimix in their main cylinders, 32 percent nitrox for a travel gas and 100 percent oxygen for decompression stops.

The Accident

As the divers descended to the wreck, Antonio's primary dive light failed. He had no backup, but decided to continue the dive. When they neared the ship's rigging, Antonio became entangled in heavy monofilament line, and it took Juan several minutes to cut him free.

When the divers finally reached the deck, Antonio discovered that he was down to just 500 psi on his primary gas mix. The stress of the mishaps had elevated Antonio's anxiety — and his breathing rate — to unacceptably high levels. He needed to ascend immediately.

Juan realized they didn't have time to swim back to the anchor line, so he immediately deployed a lift bag to serve as a surface marker and open-water ascent line. The line became fouled in Juan's gear, however, pulling him up an unknown distance before he could cut himself free. Returning to the wreck, Juan was unable to locate Antonio. After a brief search, he had no choice but to begin his ascent and decompression profile.

The Rescue

Apparently panicked by Juan's problem with the lift bag, Antonio lost all control of his dive. According to his computer, he dropped to a maximum depth of 230 feet before ascending directly to the surface, omitting at least 39 minutes of required decompression. Surfacing down current from the boat, Antonio was already suffering the symptoms of a massive DCS hit when he signaled the boat crew for help.

A field neurological exam showed that Antonio was totally paralyzed below the waist. The boat crew immediately placed him on oxygen, contacted EMS and notified the chamber of an arriving patient. When another diver reported Juan was safely decompressing, the captain signaled another charter vessel to wait for him while Antonio's boat raced to the dock.

EMTs rushed Antonio to the local chamber, where he immediately underwent hyperbaric oxygen therapy. After a series of six treatments, Antonio regained the ability to walk, but only with assistance. He has persistent partial paralysis that will likely never be resolved, as well as bladder control problems and sexual dysfunction.

Analysis

These divers violated several rules of technical diving, including the first and most important one: Any diver can call a dive, at any time, for any reason. When Antonio's light failed and he had no backup, the dive should have been terminated. Lack of light at depth almost certainly added to Antonio's anxiety level and caused him to become entangled in the monofilament line. The entanglement was another point at which the team should have called the dive —or at least checked their gas supplies before continuing.

Both Antonio and Juan failed to follow the rule of thirds, a gas management technique where divers use one-third of their gas to ascend and descend, use one-third to explore the site, and hold one-third in reserve for emergencies. Had they followed their training, the team would have turned the dive well before Antonio reached 500 psi in his main cylinder.

Antonio's severe injuries were caused by omitted decompression, even though his regulators were functioning properly and he surfaced with 500 psi remaining in his travel cylinder and 1,200 psi remaining in his oxygen cylinder — enough to complete at least some of his required stops. In this case, Antonio's panic made him forget his training, causing him to rush to the surface.

Lessons for Life

• Technical diving, like any form of diving, is safe only if the rules are followed.

• On any advanced dive, the rule of thirds must be used for gas management.

• When a primary piece of equipment fails on an advanced dive, the dive must be terminated.

• When you have problems that raise your anxiety level, terminate the dive.