Upvote:1
As I'm now in Cairns, just back from a liveaboard, the answer is - it depends!
Specifically, it depends on the kind of trip you want
If you're after a short trip (just a few days), to one of the nearby bits of reef, and/or you want to do your Open Water qualification, then you can wait. There are quite a few boats aimed at beginners, running short-ish trips, and all the backpackers / tourist booking offices had signs up offering trips departing basically immediately, with some pretty good prices. As long as you don't mind exactly when you go, and you're happy with a boat like that, even at Christmas / New Year you can probably haggle.
However, if you want to do a longer trip aimed at more advanced divers, then you need to book a long way in advance. The boat I was on (minimum open water with experience, advanced qualification recommended) which went out to the coral sea and the ribbon reefs was fully booked for around Christmas / New Year by early June! There were a few cancellations that allowed a handful of people to book on in October, but basically these sorts of boats need booking ASAP. The staff mentioned that their next open spot isn't until February, over a month away! If you were to turn up in Cairns and try to book onto one of these well-reviewed advanced boats, you're going to be disappointed.
So, it all depends on the kind of dive trip you're after
Upvote:3
Unless you are so flexible that you can go home before the 20th Dec or arrive after the 6th January, I would consider your travel high-season and likely to be full early.
From my experience trying to book remote diving locations or stays in more famous destinations is that during holiday seasons everything is extremely packed in Asia and has to be booked sometimes 6 months in advance or even more if you require a certain (cheap/expensive) type of room or specific dates. Asian countries often have less holidays than western countries and less long continuous vacations on top of that. This causes extreme overflow of people on international holidays such as New Year, Chinese New Year, Easter and so on. the fact that a lot more mainland Chinese tourists start traveling extensively, and also started diving does not help.
As an indication you can try the next upcoming holiday (in this case Easter) and see how many places are still free on the chosen destination. Please take into consideration that the Reef might be in a better/worse season in April than in Dec/Jan when it comes to weather, visibility, currents and temperature.
Upvote:3
Some friends and I went to Australia during almost the exact same time period two years ago. To be honest, diving the reef was too important to us to even think about waiting until we got there. We booked a 3 full day trip through divethereef.com, and we felt like we got a great deal.
I think we paid something like 500 USD which included double cabins on the boat for two nights, food for three days, all of the diving equipment, and 7-8 dives per day (including night dives with chummed waters for sharks!). It sounds like a lot of money, but it is about what you would spend just to stay and eat in Sydney for the same time period so we felt like we got a good deal. If I had to do it again, I would think about spending $800 to stay for 5 days on a smaller, more flexible vessel.