I almost drowned in one of these wave pools as a teenager and I had been swimming every summer in swim camps (so a decent swimmer).
In my case it was because there were so many people in the pool that I could barely move, after struggling to breathe a few moments I had to exert myself to climb up someone else's inner tube to gain my breath. But I do recall spending most of my time barely above water and struggling to breathe. Could have gone very bad.
How would you rater you 7-yo swimming ability when this happened? For example could he swim 20 meters (~60 ft)?
Also I might watch that Netflix thanks. I don't go to Bondi much but Manly beach a few km away is interesting. They are always yelling at people who are swimming in the dangerous current area and it takes several whistles to get them out. I usually give 'em a gentle yell too if I am there on a surf board :-)