BMI as I understand (open to correction) was originated as a means provide a guide for medical drug administration.
BMI has been refined using different calculations for men and women and defining if you are athletic or not.
A better judge is obviously body composition where muscle mass, fatty tissue mass and bone mass are all taken into account. At teh end of the day each person knows what sort of shape they are in, we might deny it to ourselves, but in reality we all know if we should get into better shape or not.
None of this counts. Whether He'd been a top line athlete or not, I wouldn't have allowed him on one of my boats, purely because of the risk he posed.
In the event of an incident we could not have recovered him. This is born out by the "facts" in this case where a number of boats needed to provide assistance.
While agencies differ slightly, they all teach that in the even t of a diving incident you get the causality onto the boat or the shore ASAP so you can start CPR and O2 administration. The sooner you start the better. And while in this case you don't know that if had been possible to give immediate CPR the victim would have survived. It's a fair guess that being in the water for 30 mins pretty much prevented their recovery.
People make a big thing of it being their own responsibility. While they may think so it's not always true. Families often demand closure which may mean they take out a legal case against the operator.
A case in point was Death of Lex Warner in 2012.
Mr Warner crossed the dive deck in full gear (rebreather, Deco and bailout cylinders) while wearing his fins. He slipped and fell.
He was asked if he was okay, it was suggested he not dive, but he insisted he was okay and dived. Things went wrong at 88m and he died from an internal abdominal injury.
After the investigation which identified a lack of risk assessment for fully dressed divers cross teh deck, even though PADI and BSAC identify it as a risk (and the diver would have known) The widow launched a legal action - which was unsuccessful. At teh end of the day the diver in this case was responsible for his own actions and decisions but his family still wanted to "make someone pay"
This is why operators need to take precautions for their and their customers benefit
Marine Accident Investigation Branch Accident Report
Legal New report of dismissed case