I think we need to recognize that there is a biological element involved with panic, and that is CO2 retention. Many people do not realize that the panicky feeling that they get when they stop breathing for a while is caused by CO2 buildup and not from a need for O2. Divers who build up CO2 in their systems are prone to irrational panic. My nephew's mother-in-law suddenly panicked on a dive, discarded her regulator, and bolted to the surface. It turned out her heart attack had interrupted the blood flow, which caused a CO2 buildup, which caused the panic and the sense that the regulator was not delivering air.
I was once helping a student descend into the deep area of the swimming pool for the first time. He had done fine on the shallow water skills, but he was having a lot of trouble equalizing. I was right next to him, signalling suggestions to help with the equalizing, when he suddenly yanked out his regulator and had a full blown panic attack. When we talked about it, he had almost no memory of what had happened. He did not realize he had pulled out his regulator. He admitted (should have told me sooner) that he was prone to panic attacks coming out of nowhere. I asked about it, and he said they normally came when he was concentrating hard on something, which is what he was doing on the descent in the pool. Clued to a solution by the discarding of the regulator, I asked him to think about moments like that--did he tend to hold his breath while concentrating? Yes, he did. We worked on good breathing technique (diaphragmatic breathing especially), and he had no trouble with the rest of the class. He was even feeling buoyant about the possibility that he had cured his panic episodes.
In diving, some new divers use poor breathing technique. They tend to breathe in short, shallow breaths, off the tops of their lungs. I had one student who in the very first pool session was beginning to panic every time we tried to do skills. She also complained that her regulator (a very high quality piece she had purchased for the class) was not working properly. I checked it and found that it worked beautifully--breathing was effortless. Then I watched her breathe under water. I told her that O2 intake was most effective when the air has time to reach the lungs before being exhaled. Just a little breathing technique work solved her problem--no more panic.
I now make proper breathing instruction a focus in the first part of my scuba instruction.
