Doc Intrepid:
A dive Team that plans, rehearses, and then executes a complicated penetration must function as a Team for the Team to survive. If, deep inside the penetration, one member suddenly goes into convulsions (from some medical or pharmacological malady) it is an issue for the entire Team, not merely the convulsing diver. In the gravest extreme, such an event may put the lives of the entire Team at risk - depending on the circumstances. Think silt-outs, lost lines, buddy separation, response plans in confined spaces, etc.
You might note that no team would consider such a penetration unless they knew each other pretty well and had trained together, etc. Agreed, but not many divers discuss a family history of epilepsy (for example) on a routine basis.
IMHO, if you're picking up random dive buddies on some charter for recreational NDL diving, as Genesis noted its a good idea to let your buddy know if s/he may need to respond in some way that requires - say - rescue training. But a dive Team is an entirely different case. People have a right to know if you have a condition that ultimately puts their lives at greater risk (than would be the case if you didn't have such a condition). If its only your own life, that's one thing. But you have no right to endanger the Team by withholding knowledge of some disadvantageous circumstance.
Doc
I agree with you Doc,
but in the situation posited you'd already know that, as you're diving as an integrated team.
If you show up at a cave site and do a "pick up" dive, just as you might do on a boat, then IMHO you had better be able to deal with what you get - or dive solo!
This is one of the reasons that most of the time I do dive effectively solo - I may have a "buddy", but effectively, I'm solo. Why? Because we don't do the "unified team" thing often enough for me to consider us a unified team.
You don't get that label by jumping in the water once or twice, as you've noted. You do it by training, planning, and executing dive(s) together. Thati s a relatively complicated thing, it takes time and training, and it doesn't happen overnight.
IMHO you simply are never such a team if you get on a boat (or drive to some site) and grab someone to dive with. You may call yourself "buddies" for whatever reason, but you're not "team diving."
Frankly, I wish we'd get rid of the entire "buddy" thing. It lends people a false sense of security. I have no issue with diving as a unified team, but that's
not the same thing as calling someone your "dive buddy."
I think we'd be better off if we taught people from the get-go that they should be self-sufficient in the water for typical OW diving, and that while a buddy is nice, its kinda like a set of suspenders - the belt is enough, but suspenders can make it nicer. They can also, however, pull your pants uncomfortably up in places where there shouldn't be squeeze