I'm pretty sure if you took a pic of your kid in the pool in your back garden then you're not likely to get arrested anywhere in the world!!!
If you did - well WOW!!!
And certainly wouldn't expect that in Oz... I mean for starters, how the 'eck would anyone know you took a pic of your kids in the privacy of your back garden? Nosey neighbours?? Tell em to, ahem <insert expletives here>
Now, publishing pics of your kids might be something different I guess. If you're sharing these pics with friends on social media sites, then again, the decision is yours. Heck even if you were doing it on a commercial basis - surely the decision was yours as a parent to have done that.
Again, I come back to the whole - if it's not your kids, then yes you should get into trouble!!
Very surprised that the Oz government actually passed a law like this - are you sure it's not a little more complex than how simplified you have portrayed it?