Absolutely terrifying for the DM/Instructor.
Nice save, you couldn't pay me enough to do that
This video has been around for a while, and I have commented on it before. I believe most people have misinterpreted it.
1. The video begins with a group of divers swimming at the same depth while at least roughly neutrally buoyant.
2. The camera shifts to a diver diving the thumb to end the dive, and then sweeps to others responding with the thumb. Everything seems fine.
3. The camera sweep then shows one of the divers at a considerably deeper depth then she was only seconds before. She is no longer neutrally buoyant and is very much negatively buoyant. She is waving her arms in an attempt to ascend.
4. During that ascent, she panics and removes mask and regulator.
Here is my interpretation.
1. In her OW class pool sessions, she had been taught (as many instructors do teach) to dump all air from the BCD prior to beginning the ascent. This works just fine with a 3mm wetsuit in a pool or in warm water resort diving with minimal weight.
2. It does not work in a heavy wetsuit with significant weight. She dumps her air and immediately begins to descend.
3. Lacking experience, she tries to swim up without inflating, as she was taught in her OW class.
4. Her hard work in her struggles causes a rapid CO2 buildup, and a CO2 buildup is what brings on panic. (When someone holds your mouth and nose and you feel panic, that is the CO2 talking.)
5. The CO2 buildup creates the illusion that she is not getting any air from the regulator, so she gets rid of it.
The solution, of course, is for instructors to teach students to vent air on ascent a little at a time, as needed, rather than dump it all at once. I once heard an instructor teach dumping all air to a class, an instructor who never dived anywhere other than the tropics. I once heard a DM on a boat in Belize say the same thing to the people he was guiding. I once had a new AOW student do that with me. She was wearing a 7mm suit, and I was able to catch her quickly when she sank. I asked her if her OW instructor had taught her to dump all her air prior to ascent, and she said he had.