Late Feb early March is prime summer conditions at Byron Bay. Water temp is around 24-26c and generally its the best time of year for Viz. This time of year we get large numbers of Leopard Sharks (aka Zebra Sharks) and Manta Rays.
I personally would look at travelling to Byron Bay via South West Rocks from Sydney. SWR is about 4-5 hours drive north of Sydney and Byron Bay is another 4-5 hours North of SWR (or 2.5 hours drive south of Brisbane). SWR has Grey Nurse Sharks in numbers and also has a sea cave which is 120m long which goes straight through the island of Fish Rock which is the local dive site. Water temp is about the same as Byron with 24-26c and vis can get up to 40m+. This year they had schooling Hammerheads. This drive will take you through alot of pretty countryside for the non diver and give you the chance to dive a couple of the best dive sites in Australia and gives you more options to choose from if the weather goes bad and not having all your eggs in one basket.
Diving both SWR (with SWR Dive Centre) and in Byron Bay is that the dive shops go out everyday during that time of the year depending on the weather. Alot of other shops on the East Coast do limited week day diving or only weekend.
Great lighting on the dragon, Marc. Two strobes inward?
Larry from memory it was my two Ikelite ds161 in close and angled slightly away from the dome. There was a fair bit of partical in the water. The best thing about the Tokina 10-17mm on that trip was I could shoot Leafy Sea Dragons and the next day shoot GWS.