1) IT COULDN’T HAPPEN TO ME!
Amy was a professional dive-guide. At the time this incident occurred, she had been working in diving for 12 years and had logged well in excess of 2500 dives.
She was on holiday, diving off the island of Halmahera in north-east Indonesia. It was the first dive of the day.
She slipped her gear on in the boat, did her usual checks and back-rolled into the water. She had a problem descending at first, so exhaled a little more fully than usual, ducked headfirst below the surface and kicked down.
Amy was doing a muck-dive on a sand slope, and she was concentrating as usual on trying to find stuff.
Fifteen minutes into the dive, at a depth of around 30m, her tank-valve started banging into her head. This was a bit annoying, so she took her gear off, adjusted her tank-strap and put her gear back on.
She set off again, but soon started finding it hard to breathe. “Damn it,” she thought, “this is going to be one of those irritating dives when everything goes wrong.” She tried switching to her octopus, but it was breathing hard too, so she switched back to her primary and kept going.
Then she checked her pressure-gauge. She didn’t think that she had an air-supply problem – after all, she was still less than halfway through her dive. She was just making her usual routine occasional check.
The needle was at zero!
“Hmm, I need my buddy,” she thought. Fortunately, he was nearby taking pictures and proved to be a very capable dive-partner.
He had air to spare and escorted her to the surface without any further drama.
What had happened?
When Amy got back to the dive-centre, her first mission was to find out what had happened. Apparently, the staff on the boat had not changed her cylinder overnight and she had gone into the water just with the 80bar or so remaining from her last dive of the previous day.
Although the dive-centre had made a mistake, Amy accepted that the responsibility for her running out of air was hers alone, completely.
She said that, before this incident, if you had asked her if she always checked her air before entering the water, and then again frequently during the dive, she would have categorically said: “Absolutely; 100%, every dive!”
Well, apparently not! She concluded that, possibly because her air-consumption was always better than anyone she ever dived with, over the years, without realising it, she had lost the habit of checking.
In addition to failing to check her gauge, she had completely missed a number of warning signs that, given her experience, she should have picked up.
The reason why she had difficulty in making her initial descent, and why her tank-valve started banging against the back of her head, was that the air in her tank was low and therefore the tank was more buoyant than usual.
Finally, she started to have difficulty breathing because the air-pressure in the tank had dropped to a level below that required to enable the regulator to work properly at depth.
Looking back on the episode later, she wondered why, despite these warning signs, it did not dawn on her earlier that she might be dangerously low on air.
She could only think that it was a combination of narcosis at depth slowing down her thought processes and, as mentioned earlier, her subconscious (and misplaced) confidence that, with all her experience, she could never experience an air-supply problem.