You are making assumptions. The biggest reason I want to be able to reach my valve is because of an incident my instructor had (here comes the "he is a bad instructor)
He had his rig all set up and his air turned on. Something happened, I don't remember what, that had him turn his air off. Before he went overboard he looked at his gauge and had full pressure, with the valve off. Then as he was descending he got a few breaths from the residual pressure. Now that his suit was compressed and he had little to no air in his bc he couldn't take another breath. Luckily for him he managed to turn his tank on.
This is why I watch my gauge and take a few breaths from my 2nd stage as the last thing I do every time before I go over. Still, I want to be prepared for a time when I forget to do this as well as having my valve off. No it's not likely, but I would be more comforta me knowing that I can reach my valve, if possible with my gear configuration.
In regard to the douchey #5 comment, which I'm sure you will say was from a place of genuine concern. My first reaction in a situation like this wouldn't be to reach for my valve, it would be to reach for my redundant air source. Then if I can easily reach my valve, I would turn it on.
Do I think reaching my valve is the most important thing I shoul focus on? No. It would make me feel safer if I could though, and possibly save my life/weightbelt/rig.
Nothing in my post was directed at you, especially on a personal level. The "you" was the general impersonal "you" like the word "on" in french that is used to indicate a general impersonal "you" or "we". But I have been called worse things than "douchy" in my life, I am a retired naval office.
That being said.....I think you (the personal "you") is on the right track by taking a couple of breaths of your reg before hitting the water....that is the general idea....it should be done during the buddy check while looking at the gauge to specifically see that the tank valve is open and gas is flowing properly. It is prudent to do it again before entering an environment that we cannot naturally survive in. Being able to reach and turn the valve does not ensure all is OK.....breathing off the reg and making sure that it works effectively does.
About your instructor....I keep reading about incidents posted on SB and perhaps its just the threads I am reading or perhaps its reality but it sure seems like the people that are having the most problems are those with high levels of certification....sure people screw up, and **** happens....karma is a muthaf#$@er....but I believe in the notion in the quote: "fortune favors the prepared". Where was your instructor's dive partner...was he teaching a class? if so did he have a safety diver present looking out for his well being since his students would be unreliable at best? How many instructors enter the water a group of new divers without a safety diver for themself? From what you described it seems like he shut his air off before he donned his equipment....the buddy check is supposed to happen after equipment is donned; had that happened perhaps the valve being closed would have been caught and the problem averted altogether, or perhaps in demonstrating to his buddy that he had however much air and both his 2nd stages functioned while observing the needle on the gauge, he would have observed that his air source was not functioning properly and the problem would have been caught and the issue he experienced averted.
The dangers of diving remain constant and immutable. The only thing that changes is our perception of those dangers and our attitude/mentality towards them. If you (the impersonal "you") believe that a dive is just a routine dive becaus you have lots of dives under your belt and/or you have dived the site many many times, or for any reason, then you are succumbing to confirmation bias, which is a dangerous precedent to operate under....you may not have an issue or you may not come back alive. How often do we see other divers acting complacently? On a recent dive with a club I am a part of I was paired up with the teenage daughter of one the instructors in the club....as we were doing our buddy check he walked up to us and told me to hurry things along because it was hot out and his daughter might be uncomfortable in the heat decked out in wetsuit, hood, etc. I believe this to be incredulous and it is a problematic mentality that pervades the world of diving, I see divers taking shortcuts all the time.
And for the record, I have never stated that this not a good skill to have....I agree that it is a good skill to have, it is a useful skill to have, I stick to the notion that it is not a critical skill, and I believe that the major certifying organizations for recreational diving, SSI, NAUI, PADI, etc would agree based on the fact they do not include this skill in their course fundamentals for basic and advanced open water certification. I contend that some who have participated in this thread have inflated the importance of this particular skill and cite
incidents that could have been avoided or dealt with more effectively through prudence, forethought, and adhering to the standards which they were trained and certified (acknowledging that the quality of instruction varies...but each student should receive course material to supplement the instruction).
-Z