I did not know him personally, though I'm sure we've met online here. Indeed, a tragic loss, as a diver, this is the most horrifying & saddening thing to hear or read..
Oh John (Copps) you are ALMOST right, except on one thing, in Deep Diving the rules are close to those for Cave diving. One thing always: THERE IS NO MARGIN FOR ERROR.
Condolences to his friends & certainly family!
Sincerely,
Matthew