There was a program on this last year or so and from what I saw I have a few doubts about the guy’s guilt. If this is the same incident I saw the fatality happened on the wreck of the Yongala, not the Great Barrier Reef. In my opinion the Yongala is an advanced dive - When I dove it there was a current running, good swells, > 100 fsw to the floor. Of course it would be a simple/ safe dive for a NC wreck diver but it is my understanding this was their first ocean dive?? Also, it’s not uncommon for someone to open the tank valve partially allowing a constriction as the tank pressure dropsbailed someone out (no pun intended) for that once.