Am going to GBR April 2003. Planned to stay in Port Douglas. Did PADI OW in October 2002 & would like 4 day-ish dive package, maybe live aboard. My friend snorkels. Have seen lots of trips out of Cairns - is that a better base? Is it better to book in advance or could I get something on the spot? Thought maybe pre-booking not great idea if weather's bad (rainy season?) Any suggestions? Thanks.