i did scuba diving in qld at the great barrier reef about a year ago. went to about 12 or 13m (about 40 feet in US terms) for a first time dive. qld would by far be the best place because of the reef, but there are a few places in sydney where i see scuba diving school, La Perouse in Botany bay, as well as Clovelly in the eastern suburbs. there are a few diving schools. try
www.yellowpages.com.au and search for scuba diving, im sure you'd find plenty of places where they'd teach scuba diving.