I've had several situations. The first was my own; I had a violent freeflow from my backup regulator that we couldn't stop. I had two buddies sitting in front of me with their long hoses at ready; I took the instructor's, and we ascended. Tank was empty before we got to the surface, and we started at 30 feet. In retrospect, I wish someone had shut off my tank so I'd have been free of the noise and the bubbles.
Second was not my rescue, but I was there. We surfaced from a class dive, to find a very young man (I'd guess 13 or 14) on the surface. He was barely bouyant, and he just kept saying, "Where's my buddy? Where's my buddy?" He didn't answer when we spoke to him. His eyes were very wide. My instructor swam around behind him, came up and inflated his BC. We stayed with him while the instructor dropped to find the class of which this young man was a part. His instructor hadn't noticed he was missing. He was in total, completely disabling panic. It didn't look at all like what the video scenarios show.
Third was a real rescue attempt. I was at our local mudhole, not diving, but simply having driven an out of town visitor there to see the place. A good friend was also there on land, and we got to chatting. Looking out over the water, we saw a diver surface, and he appeared to be having a conversation with a walker who was standing at the top of the riprap slope. The walker then got out his cell phone, and we all started to trot to the area to see what was going on.
As we got near, my friend realized that the diver who had surfaced was someone he knew, who had been diving with a mutual friend of ours. I will call the surfaced diver "buddy", and the his buddy "victim". The friend we were chatting with will be "friend". Friend and I climbed as quickly as we could to the bottom of the riprap, and there we found Buddy supporting Victim. Buddy told us his friend had signaled a problem a few minutes earlier underwater, and asked to return to shore. Halfway there, he thumbed the dive. He arrived at the surface and said, "I can't breathe", and lost consciousness.
The three of us worked to get Victim out of the water and onto a firm support. Unfortunately, we did not have a beach anywhere near -- we had a boulder slope. We cut off Victim's gear (and I later decided that was foolish, because the backplate would have made a great surface to do CPR on, if we had just cut the cambands and gotten rid of the tank -- but nobody teaches you to do that, and we were following protocol we had all learned). We tried to arrange him as best we could on the rocks, but he was almost 300 pounds, and not easy to move as dead weight. Buddy began mouth-to-mouth and Friend began CPR. Buddy was an EMT; Friend was an EMT, and I'm an ER doc.
As often happens when people are dying and getting CPR and mouth-to-mouth, Victim vomited, and Buddy got a mouth full of it. He bent aside to vomit in his turn, and returned to doing ventilations. (Buddy was one of Victim's best friends; they had known one another for many years.) We traded off CPR, but CPR isn't very effective on people that size, and especially not on uneven and unsupporting surfaces.
Since the walker had called 911 and our major trauma hospital is only about three or four miles away, it wasn't long before the paramedics got there. They faced a tremendous challenge in getting this man onto a board and up this long, very uneven and difficult slope to the sidewalk. Doing adequate CPR and ventilations was nearly impossible, although they really tried.
At the top of the slope, they continued; they intubated him, and I don't know what his rhythm showed. They transported to the hospital, where he was declared dead.
What I learned from this: Accidents don't always happen on deep or risky dives (this one was shallow and VERY familiar to both divers). They don't always happen where it's easy to get someone onto the beach or boat and help them, and they don't always happen to people who are easy to move around. All you can do is the best you can do and hope; Jake, we did what we could for you, and I still miss you.
But that's a whole different can of worms!!
