Fear, fight or flight response, or other mental activity that distracts from problem solving and corrective actions wastes valuable time in a real crisis. IMHO, one of the greatest values of experience is to minimize overreaction so an inconvenience doesnt escalate into a perceived crisis.
The only personal crisis (excluding major physical trauma) that demands rapid, not necessarily immediate, action is oxygenation. I believe it is a primal reaction to take frenetic action at sudden lack of breathing gas, at least past the early newborn range. It probably served evolution well in that it can repel attach or get your face above water, at least for a short time.
Unfortunately, if my hypothesis is even remotely correct, this bit of evolution does not serve divers well. Most forms of crisis training are highly dependent on habituation as a key component. Habituation is not necessarily achieved in training or from experience as recreational divers know it.
My recommendation to a disciplined individual who hopes to become a great diver is:
1. Master buoyancy, not as a diver but as a swimmer: Understand that the only thing that needs to be above water during the times you are actually breathing is your mouth and maybe your nose. Any other part of the body, especially the high density skull, that is above water is a waste of energy.
2. Master swimming: You dont have to set speed records or learn all the strokes; you are after endurance. The value here is knowing that you have plenty of time. An embarrassing number of diver drownings occur on the surface. It is incomprehensible to me how anyone can drown in a wet or drysuit at or near the surface. DUMP WEIGHT!
3. Learn basic diving physics and physiology: Pick up a book or video to learn about pressure, gas compressibility, displacement & buoyancy, and principals of oxygenation. By this time, much of it will reinforce what you have discovered in earlier steps. Dont worry about decompression, embolism, and oxygen toxicity at this point.
4. Learn to snorkel and freedive: You can learn to snorkel from friends and gain a lot of experience. When you feel ready, pay the big bucks for a good freediving course. You will learn how to safely extend, test, and learn, your limits. Tell the instructor you want to experience hypoxic blackout under their guidance. Pool static training will give you ample opportunity. Again, the end objective is to learn you have time.
5. Buy an old used regulator and Scuba Tank: Put a paint-ball sticker on it if you have to in order to get it filled. Take the second stage apart and see how it works. Really play with it. Just dont take it in the water yet. Try to take apart and reassemble the first stage if you are mechanically inclined.
6. Take Scuba courses through Nitrox, add rescue if you are inclined. Diving Nitrox is not the objective, gaining the in-depth understanding of diving physics, and to a lesser extent physiology is the goal. In the process, find an instructor who will guide you through free ascents starting in a swimming pool and graduating to as deep as you like. Avoid instructors who view BCs as elevators, free ascents and dangerous, and self-learning as lost income.
IMHO, this process will give most people the habituation, education, and most of the experience to make you self-reliant, confident, and capable. Individuals with the discipline and dedication to follow this path are also likely to become highly competent divers in a relatively sort number of logged dives.
This foundation will serve you well regardless of how much farther you want to go. At that point technical diving, rebreathers, or commercial diving through saturation becomes far more about mastering systems than diving.
