A great article to read:
Diving into Scuba Litigation - Maryland Physician / Attorneys, Merck, Heart Attacks, Strokes - Lawyers
Bottom line is that it can get complicated and anyone can be sued for any reason.
Wow! I read the whole thing (which I have seen before) and don't see anything in there that would lead anyone to draw the conclusion you did. The only examples of actual lawsuits it cites are to professionals acting within an agreed professional relationship.
It does go into theory on what
might happen (but never has) in a buddy relationship.
If one diver runs out of air, the buddy must share his or her air supply. If a diver becomes tangled in debris, the buddy must assist in extradition. If a diver becomes cramped or incapacitated from exhaustion, illness, or injury, the buddy must provide assistance, without unreasonably placing himself or herself in danger. If a diver is panicking and can be approached safely, the buddy must try to make physical contact and get his or her buddy to the surface. Buddies who panic or refuse to help where it is feasible and safe to do so may be legally responsible for their partner’s injuries.
Two years ago in Australia, Gabe Watson pleaded guilty to manslaughter in the death of his wife. In pronouncing sentencing, the judge went beyond the plea deal and said that Watson was guilty of manslaughter because he failed to come to the aid of his wife, who as his designated buddy. There is a thread on this on ScubaBoard, and the attorneys who participated in that discussion were amazed at this because there has never before been a decision that said that anywhere. There was some concern that this would set a precedent, but the attorneys said that under Australian law, a court case settled by a plea deal cannot be used as a precedent.
Key Point: There is not a word or phrase in that entire article that indicates that a professional diver who is not acting in a professional relationship might be sued. If you still believe that this article supports your belief that the "Bottom line is that it can get complicated and anyone can be sued for any reason," please indicate one sentence that suggests that.