I'm not clear about the overhead environment in this case; can you explain something for me? "Open water" means an unobstructed route to the surface at all times. Even if there's a natural "bell" meaning air above water surface in a cavern, you still have to travel under a ceiling to get to it. Is that an accurate description of your environment on that dive? IOW, was there any point during the dive at which you did not have an unobstructed route to the surface?
If the answer to that is "yes, there were points.." then I would think that the instructor and/or shop that ran the class would be in serious violation of any OW certification agency. Even if this environment does not technically qualify as an overhead environment, I believe it's very poor judgement to take an OW class into a situation which at the very least violates the spirit of OW training and sends a very poor message to the students regarding safe diving practices.
Something just doesn't make sense to me about this whole scenario, because I find it hard to believe that an agency-sanctioned class (or instructor) would do what you seem to be describing. If I were in your shoes, I would immediately contact an attorney to look into this. At the VERY LEAST, the shop should pay your medical expenses if in fact they took you into an overhead environment on your OW certification dives. Maybe that would motivate them to stop this extremely dangerous and irresponsible behavior.
The other thing that I'm having trouble understanding is why you did not simply reach for your octo or alternate 2nd stage. I clearly remember in the pool sessions for my OW class being drilled to practice switching to the alternate on numerous occasions. I've even seen that done on "discover scuba" classes. I'm sure the first time you're in the situation of really not being able to breathe panic will set in quickly, but still, you should have developed the critical skill of simply reaching for your alternate. I'm sure you're practicing that religiously now!
I'm impressed that you immediately continued with your diving; most people in this situation would probably move immediately to Kansas (not that there's anything wrong with that!) or some other landlocked state and never go near the water again. Good luck to you, and please investigate what appears to be a very disturbing practice by your dive shop. If I've misunderstood your description, then take my advice with a grain of salt. As I said, I feel like I must not be understanding something, because I can't imagine a shop or instructor doing this.
