I have a few:
1. A friend (no, really - it wasn't me) was given a torch at the entry of a swimthrough on a 50m air dive. At the other end of the 8 metre swimthrough, when asked to return the torch, she denied every having it - and continued to deny it after the dive (loss of memory). We went back to the site the day after and found the torch in the sand at the entry to the swimthrough, still on (although now flat). Seems she just dropped it there and totally forgot ever getting it.
2. The same person, on an air dive to 70m, went unresponsive at about 60m, losing all buoyancy control (to arrest her descent) and drifted slowly down to the target depth. When another diver went to assist her, she (accidentally) knocked his mask off while he was inflating her wing. She didn't regain awareness until ascending back to the 21m stop/switch, and to this day (AFAIK) cannot remember anything from the time in between (apart from a vague recollection of sinking and her mask flooding). Back on the boat, she burst into tears spontaneously.
We didn't take her on any deep dives after that
3. Me this time... on my first ever "tech" (deco/accelerated deco) dive to 41m, I had a classic happy narc - maybe the most 'fun' dive I ever had, but the run time I had on my slate didn't make the slightest bit of sense to me until we got back to 21m or so. I just followed the other divers, luckily they were following the plan, so yes it ended up being a 'trust me' dive. I did manage to monitor max depth and max time but that was about it, otherwise it was just 'yipee!!'
4. Me again... I was a little light at the start of a 45m air dive and had to work to descend. Obviously this was only going to get worse on the deco stops after using some gas in the dive. At the target depth we found some lost weights but discarded them after they were too heavy to comfortably manage at the target depth. Didn't even think that at least one would be handy for the later stops, until I was at 6m breathing *very* shallowly to hold the stop
I've been mcuh deeper and felt less dumb, which just goes to show what the other posters have been saying
I've also had visual and auditory 'hallucinations' never seen any dead people though