Dive operator in Sydney area

I have some friends traveling to Sydney on business. Well, she's
traveling on business, he's tagging along. They'll do a week in
Cairns (probably) but he'd like to do some diving in the Sydney area.
So I'm looking for a good shop there. Also, I seem to remember the
water temps being a bit on the cool side. How much of a wetsuit would
he need to bring?

Any suggestions on operations other than those around Cairns? They
don't have their hearts set on there, it's just what they've read.

Thanks
--
dillon

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