You must do Lady Elliot Island at the southern end, too. It is most impressive and full of turtles and manta rays.

Enjoy!

Lizard Island – exclusive and expensive but very nice.
Green Island – boat access from Cairns, day trippers and stay available.
Heron Island – boat access from town of Gladstone, a reef surrounds the island. Good size resort. Also has Reef Research station.
Lady Elliott Island – a few ways to get there.

Google for these island resorts and there is all the information you will require. It is worthwhile to stay on one of these. Otherwise from Cairns / Port Douglas there are day trips to the reef, where you will spend a few hours snorkeling if you do not have the time.

Like any reefs worldwide, there are times that coral bleaching occurs, but, this can be a normal process to a certain degree. The reef is SO extensive, not ALL the reef is experiencing this all the time. The biggest threat to the reef is from our cyclonic storms, which causes immense damage to corals by the strong winds. But one gets plenty of warnings if these are on the horizon. The Great Barrier Reef is not one reef, it is is huge series of reefs, islands etc. and is pretty far offshore for much of its length.

Also, it’s sad to hear that people around the world think there is a problem.