Beside drinking & diving, the dive preparation & plan were disturbing, from reading the statement, below,
“He’d borrowed dive gear from Smyth for the day, and when they got in the water, they checked each other’s equipment for leaks, and then secured an extra dive tank at 5m if they ran short of air while returning to the surface.
Around 4pm, they began descending the anchor rope, and when they reached 50m, Smyth, who was wearing a dive computer, signalled to Pattinson to stop. Pattinson indicated he was okay, and agreed when Smyth motioned they should start ascending.
That was when the school of kingfish appeared, and the divers became momentarily distracted.
It was only when they’d passed that Smyth noticed Pattinson had carried on descending, and was now well below him.
He followed his friend, but knowing the regular air they were breathing would turn toxic below 60m, Smyth eventually had no option but to leave his friend, and kick for the boat as fast as he safely could.“
It sounds like, only Smyth was wearing a dive computer. He should have led the dive and descent first. He’d be more in control of the situation.
Since Pattinson was borrowing Smyth’s diving gears, he may not be wearing a dive computer and was not aware the depth he was in without a dive computer to alarm him at 60m. He seemed to be a less experienced diver of the two of them and he should stayed above Smyth and followed Smyth’s direction. At least Smyth would have stopped & blocked Pattinson from descending further if Smyth was below Pattinson.