Mr Higgins says cave diving is more rigorously policed here. All advanced caves in Australia are under lock and key, and who gets the key is controlled by the Cave Divers Association, in which he is an advanced cave instructor. He says safety is a priority. Even after you've completed a cave-diving course, it still takes at least three years before you're allowed to attempt the advanced caves.
The association's official position is that it is opposed to solo diving, that cave divers should be with a buddy - although individuals have differing views. It has emerged that Ms Milowka was solo diving last Sunday.
Mr Higgins has previously done solo diving himself and says it can be done while minimising the risks. ''But you're never going to eliminate all risk, or with anything that you do in life.''
Steve Trewavas, national director of the Cave Divers Association, says it appears that she breached at least a couple of guidelines. Solo diving is one, and the circumstances around which she was diving solo remain unclear.
Another is the use of marked lines on intercepting lines within the cave. If you come to an intersection where there is another line, you're supposed to mark the intersection with an arrow indicating the return route so you can feel your way out.
''She probably went over at least eight or nine intersecting lines which she never marked,'' he says.