Longform

Rebreathe Deep the Gathering Doom

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With its abundant sea life, it's an ideal place to spearfish, but Zak Jones no doubt knew that he was breaking the law when he plunged into the water wearing a Megalodon system and carrying a spear gun. Spearfishing while diving on a rebreather can be punished with jail time and hefty fines. It's just too easy to prey upon underwater creatures when you aren't bubbling, according to the Florida Fish and Wildlife Conservation Commission.

But Jones, the only diver using a rebreather that day, was willing to take a few risks.

On the bottom of the sea, Jones and buddy Richard Hartley — vice president of the Pro Dive training department — parted ways in a common but unsafe move. Hartley told the medical examiner's office that they split off so Jones could spearfish without risk of skewering his friend.

Sometime later, Jones caught the biggest grouper of his life. His father, David Jones, says that the two had speared ten- and 20-pounders on their fishing trips but not a 50-pounder. Jones' adrenaline probably went through the roof as he wrestled with the monster and subdued it.

And it's possible that those exertions put Jones into danger. Breathing faster, Jones might have been dragged deeper by the fish, and that may have affected the level of oxygen in his loop — what rebreather divers call their closed system of gases. His fight with the fish might also have taken his mind off his rebreather's heads-up display, a warning device that flashes green, then yellow and finally red directly into a diver's eyes as oxygen pressures go into dangerous levels.

But Jones' Megalodon showed later that he had set the oxygen levels correctly for his depth — 1.3 bars of pressure — which should have caused the system to add oxygen at a correct rate.



Still, for some reason, nearly 200 feet down, Jones became so concerned about the gases in his rebreather that he decided on a radical action — to bail out of his loop.

Hartley, after seeing Jones with his fish, was away from him again for several minutes. And it was during that time that something went so wrong that Jones became convinced he had to seal his rebreather mouthpiece and cut himself off from its recycling gases.

Why did Jones reject his own equipment? That's what the experts have struggled to understand as they examined his gear.

Bozanic says that one thing in particular about Jones' Megalodon puzzles him: Although the equipment was in working order, the unit's diluent had been shut down.



In other words, one of the two sources of oxygen on Jones' back wasn't available to him. By itself, that isn't fatal or even unusual. Sometimes, divers suppress their diluent to help maintain buoyancy control. But Bozanic wonders if there's a chance Jones' didn't know his diluent was shut off. And when his system began to give him trouble, he didn't realize that by opening the diluent, he might have restored his loop gases to safe levels.

Another clue appears, at first glance, to be more ominous but may be only an artifact: Jones' other source of oxygen, the canister that carried pure oxygen, was empty when Bozanic inspected it. He says that seems strange, since Jones' dive lasted only 27 minutes, implying that he had begun his dive with almost no oxygen in that tank. Another explanation is that Jones had plenty of oxygen during his dive, but in the three weeks that transpired between the accident and Bozanic's inspection, the tank had slowly leaked away its gas.

More convincing evidence for what actually happened is a residue found in Jones' oxygen sensor pod, which tests the quality of gases in his loop. Bozanic found a powder caked on the interior surfaces that could have been soda lime, residual cleaning solution, or even salt. The powder was swabbed and stored at the medical examiner's office but hasn't been tested.

Heinerth reported that the powder may have produced a taste in Jones' mouth or could have irritated his breathing to the point of making him cough. Although an autopsy didn't find irritation in Jones' lungs, he may have believed he was about to get a "caustic cocktail," the common diver's term for the chemical burns in the mouth and lungs that occur when water gets into the loop and soda lime leaks out of its canister.

It's a terrifying prospect, and if the taste in his system caused Jones to believe it was about to happen, he may have decided to bail out before a caustic cocktail burned him.

And when he did, it was time to go to the backup systems. In parachuting terms, Zak's primary had failed, and with the ground rapidly approaching, he needed to pull the emergency chute.

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Ashley Harrell
Contact: Ashley Harrell