Gotcha, sorry I'm clueless. What I gather then, is that GBR is not really accessible from Sydney. To dive the GBR, it's easiest to be in Cairns?
Yeah, I just did it and I flew from Sydney to Cairns (3 hour flight). It worked out great. I ended up doing the Spirit of Freedom live aboard and it was incredible. By far the best diving trip I have ever had. I want to go back soooooo badly hah