Perth beaches have always been closed several times a day. When I was a kid in Perth the beeches had sirens to alert the swimmers of shard sightings. The sirens would go off 2 or 3 times a day on the weekends and that was in the 1970's.
Nothing has changed except the people had more common sense when they were diving and surfing in those days. They knew for example not to piss in the water or splash around on the surface. The surfers knew not to surf at the mouths of rivers etc. The divers knew not to spear fish and keep them on you or not to swim in the fish schools. I think there are a lot more divers now going out to burly up sharks because they've seen it on TV.
