Scuba on Carnival Australia GBR

[LPGA Golfer Gal]

Booked GBR for June next year out of Sydney. Struggling to find details on booking scuba (not snorkel) for the stops on the GBR. I have found some very old (pre Covid) information but just looking for clarity on diving the reef. 
which are the best stops or will there be diving at all stops on this trip? The shuttle out to the reef is long but there will be options to scuba dive at each stop, correct? 
This is a bucket list for my hubby who is an avid diver and with excursions not yet available to view and can only be purchased once on board I would like to have details lined up before having to make the choices at the shore excursions desk. 
Thank you.

[M-H-B]

What ports do you have on your cruise - Cairns and Airlie Beach or others?

[LPGA Golfer Gal]

, Tangalooma/Moreton, Cairns, Airlie.