That'll have to be one of the islands. I grew up in NQ and did visit the reef a few times, but always needed a boat trip to get there (we stayed at beaches on the mainland).

I'm not sure how good the snorkelling is right off the beaches on any of the islands, but don't go in the rainy season. Affects the colours of the coral if there's a lot of rain. Plus, stingers/jellyfish are a hazard.

I'm really looking forward to taking my family up one day. It is truly amazing to see.