The great barriar reef is best seen in May after the wet season has ended and water clarity is improved. I was there in January. Luckily it was much drier than ususal, not to be confused with dry like Idaho or Arizona but ok.

he great barriar reef Boats out to the reef cost about $50 USD

Giant clams in the movies snap shut on divers hands holding them till they drown. It is not recommended to touch any marine life with your hand, it is very damaging to them and possibly to you. Giant clams are the focus of recovery efforts after over-fishing and poaching in past years. But hell, if the guide says try this... Putting your hand inside the shell tough

Parrot fish are everywhere on reefs. In Australia, there are OTHER fish as well. Some damage by crown of thorns starfish, some by storms but overall, the reef is in good shape, unlike much of Thailand, like Ko Phi Phi which is "hammered".