Another place we were on Honey Moon. We spent 4 days in Cairns, 2 hours plane from Sydney.
This is a little city near rain forrest, it has several things to do here. Go to visit rain forrest, Chapukai Indigenist Reserve, Koala parks...
But the best thing you can do here is to go on cruise to swim and snoquel at the Most Large Barrir reef of the world, "The Great Barrier Reef".
There are a lot of cruises from Cairns, the Prices are between 80 A$ and 300 A$ per person, material for snorqueling included. We recomend spend a little bit more than 120 A$ in order to go to exterior barrier reef, than it is better conserved than interior one.
Here you can see the colored fishes, all around you neear the great colored reef...And incredible experience