Good tips, Deep
One thing that was mentioned was not knowing why you should never slap or yell at a person coming out of an submerged blackout.
The larynx spasms itself shut as an automatic reaction to the body shutting down in water, in the aim of keeping water out of the airway. I forget the medical term, but it wears off as the person slowly comes to, unless prolonged by further trauma that the body blindly detects.
If the "buddy" yells, slaps, or does something to try and scare the blackout victim into conciousness, it can have adverse effects. If the blackout victim's body senses more trauma (such as a frantic buddy smacking your cheeks and yelling), it will continue to try and protect itself, with the larynx still squeezed closed, and thus the airway primarily blocked.
Instead, calmly talk to the blackout victim as if you were waking him/her out of a post-operation anesthetic, blowing on the eyes until he/she draws a breath and opens his/her eyes. Soft stimulation, such as caressing the face, neck, arms and stroking the hair is a good way to let the body know that it is in a safe condition to reawake. Most people's bodies seems to inherently recognize such sociological creature comforts.
Another more dangerous setback of slapping/yelling at a blackout victim, in some of the more serious cases of longterm blackouts from traumatic situations, is that the person might go into shock. And a diving buddy undergoing shock is a whole 'nuther can'o'worms that you don't want to deal with when you're yet back on the boat, let alone on shore in short distance from medical attention.