I have heard very good things about TUSA Dive.although I haven't used them personally.
Or you could visit Mission Beach 2 hours south of Cairns and dive there.
http://www.calypsodive.com/Diving-Snorkelling.aspx about 7 years ago
I would suggest quicksilver located in Port Douglas. (07) 4087 2150 They take you to a beautiful barge about an hour out, then you have the option to swim in the netted pool, snorkel or jump on a dive boat out to thye great barrier reef. One of THE BEST dive boats I have ever been on!!
South Florida misses you!! about 7 years ago