What makes this port unenjoyable is the tender (45 minutes water time plus wait) and the 1/2hour shuttle (Celebrity doesn't pay for. $36 per couple.). Half your time in port is spent doing this. What's worse is that we overnighted there. This means you could go through the process a much as 3 times.
In Cairns we booked our own tour for snorkeling the inner Great Barrier Reef. The outer reef was better snorkeling but it took 2 hours each way to get there and we didn't want that long of a trip. We went to Green Island. $180AUD per couple. Saw plenty of turtles, sting rays and even a shark. Coral was beautiful but spotty. Glass bottom boat was part of tour for non-snorkelers and those that had their own snorkeling equipment. Island has all services including gear, jelly fish suits, restaurants and bar.
Read FrankA's full Celebrity Solstice cruise review