I am glad Rob's story had a happy outcome. I have always wondered about the statistical likelihood that recovering an unconscious diver found under water will be successful. I fear that the other scenarios I quoted above are more likely, and probably much more likely.
Truth is that non breathing, not responsive victims have fairly low survival chances even when they are not submerged unless a lot of things go right. Just add water and the statistics worsen!
Having O2 and AED on hand help a lot. In the end it is the time it takes to get them to Medical care combined with the condition of the victim that will determine the final outcome.
I've been involved in 2 events I would call rescues.
One panicking in respirator distress on the surface. Wound up stripping her of her gear and getting her to shore. Hardest thing was getting through to her to calm her down. In the end I really think it was a case of someone who really shouldn't be diving due to respirator issues. Positive outcome.
Second involved an unresponsive diver. That one was fairly "text book" search, recovery and CPR but a negative outcome.
While I wouldn't call it a rescue I also had an instabuddy go OOA. I got added to an established buddy pair. The regular buddy wound up oblivious to the fact that the diver was OOA or just didn't care as he powered away from us in rough seas. I wound up staying with the idiot who went OOA while he babbled on about how he had his DM and Rescue Certs and he could tow me in I still had enough gas to do the dive again instead I was fighting the waves as we had to go to a rather unpleasant exit point. He thought the whole situation was quite funny and was quite blase about it. I had a word or two with the Dive organiser about pairing me out with these guys when I found out the had a reputation for this kind of stuff.