It's my estimation that this was nothing but a suicide. He was killed by his own lust to be the best, the deepest. Some will find my words blunt or even brutal, but I want to put this attempt into perspective, lest others try to set that record. Of course people trying to set records, for whatever reason, tend to be unreasonable and it's impossible to reason with an unreasonable person. In any event, to paraphrase a movie quote: "Stupid is as stupid dives."
In the seventies and eighties, the Central Florida area was constantly bombarded by deaths from such attempts to be the deepest. One of the instructors in the area was even known as "Bring 'em back dead or alive ____" because of how many of his former students perished trying to outdo their teacher. A little bit later we have the death of Sheck Exley in 1994. Schek had given us the 'Blueprint for Survival', a guide that has saved countless divers from dying in caves and yet he succumbed to that Siren's call. It should be pointed out that Schek had vastly more experience than Doc Deep ever contemplated.
I really have no clue as to Doc Deep's motivation, and for this discussion, it really doesn't matter. Egomaniac or intrepid explorer: there's a fine line between the two and only the individual can honestly answer that question and even that's a crap shoot. We often see denial and delusion accompanied with attempts to set such records. I never met, spoke or corresponded with Doc Deep, but his death is proof enough that he overstepped his limits with deadly results.
That should be the real takeaway here: A diver's got to know their limitations. Again, another paraphrased movie quote, but something every diver is faced with on each and every dive. I ingrain them into all of my students: Time, depth & gas. Then there are the other limits: certs, skills, physical, mental, buddy, gear and so on. You push and exceed these limits at your own peril. It's no question that Doc Deep exceeded his limits. Only a fool would contest otherwise. There's simply no plausible good reason to turn this non-competitive sport into a competition. Such is the quest to be the deepest. Such is an attempt to commit suicide, whether that's your goal or not. I and I alone are responsible for the dives I do. I and I alone are responsible for my safety in the water. I and I alone are responsible for evaluating and honoring my limits. In the event that I die or am otherwise injured under water, please, please, please point out my stupidity to the world. Others should learn from my untimely death if only to prevent their own.
'Nuff said.