Its pointless to have a buddy if youre diving deeper than he can...the limiting factor for buddy diving is the depth of the weaker diver.
Rig, I kindly disagree. Not with the concern for being careful, but with the view of equal deepness ability. We talked a lot about the possibility/impossibility of deepwater blackout out at the Performance Clinic. The facts from the very few possible existing incidences of deepwater blackout are suspicious and just don’t hold up to science.
Black outs are the number reason for buddy diving. In deepwater the O2 particle pressure in the body is high from the compression of air space in the lungs. People black out when nearing the surface because the refilling of the lungs lowers the O2 particle pressure which tends to suck the O2 back out of the blood and into the lungs, and also because it is the longest point of the dive.
There have been a few possible cases of nitrogen effecting judgment, but that was experienced by only a few top freedivers doing record type depths. Way deeper than a breathold spearfisherman would go.
I would feel comfortable going 80’ with a buddy I knew was competent, responsible and observant if his max was only 50’. As to the closeness of the buddy, in deep water I would say as close as possible without tangling the float lines when we are going 60’ or more. Scaring fish in deep water is not a concern, because they are not very scared of someone being still on the surface.
The reason the buddy has to be close is they have to be able to get there before the diver sinks. Most divers lose their air when they black out, which can easily make them negatively buoyant. A diver who is neutral buoyant with full lungs at 30 feet, maybe negatively buoyant in as little as 15 feet with no air. As they sink the compression of their body and suit will make them more negative and accelerate their descent. If your not there in a hurry, they maybe too deep for you to recover them, no mater how good of diver you are.
If were going to push it, I think its good to have your buddy dive during your ascent and meet you at 20’ to 40’. That way there is less of a chance of you sinking before they could get there.
Don