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While any dive can kill you, the degree of risk varies (consider shallow 40 foot max., 20 foot average reef dive in benign tropical conditions with no current, vs. a deep cave penetration at depth on a rebreather, going to extremes to illustrate the point), as do options for self-rescue (e.g.: the SDI Solo Diver course sets recommended solo dive parameters such as no penetration, no deco. obligation, not pushing your limits or new experience (i.e.: pinnacle dive for you)).....
Yes, I agree - as you say it is semantics. Calling the more risky dive "advanced" is common in diving, but really it is the risk (and risk management) that is the key issue.
The only person I have seen drown first hand was a guy on a Rescue Diver course (pretty ironic). He was on the exercise where you dip down and rescue an unconscious breathing diver (role played by a volunteer in the drill). For reasons unknown the student missed the waiting diver and carried on beyond the training platform in the quarry. He (the student) was low on gas but had "enough" to complete the drill. Visibility about 3m (10 foot). Having missed the "casualty" the student began a search and ran out of gas. A situation from which he did not survive.
As a result the school changed it's procedure and required a "buddy" to accompany in water divers at all times (both the rescuing student and volunteer pretend casualty in this example). Thus for this exercise what was accomplished with the instructor (casualty) and student, now required four people in the water to complete the exercise.
The quarry environment is pretty benign - no current and the bank just a few metres from the submerged platforms specially installed for exactly such practice drills. The platforms are also marked with lines and floats to show the end of the platform. The deceased in this instance was requested to descend the line to the 6m platform where the "casualty" was waiting. The exercise would have been acceptably completed with physical contact to the line during the descent.
On the face of it the risk of letting the student (by definition an AOW diver) descend the line solo is very small. His death was a direct result of his personal decision to search for the waiting diver despite the obvious course of action to return to the surface and repeat the descent, combined with the decision not to refill the tank prior to making the dive. His body was found well below the 6m depth and the depth gauge fitted to the console was found to be working accurately. The tank was empty. He was still wearing his weightbelt when found.
I think risk is a personal thing. I think "advanced" is a personal thing. I genuinely believe that good gear configuration and team mentality mitigate a lot of risk in diving. Watching someone else make the big mistake is helpful as well. I can still close my eyes and see that blue face.
As they say on Hill Street Blues, let's be careful out there.