In Queensland, You can hire windsurfing gear in
Sunshine Coast
Brisbane
Gold Coast
Ask others about New South Wales.
You will have to collect it from the shop and pre-arrange it.
Surfboards are available for hire from every beach.
Definitely do a bit of windsurfing. It's nice warm water.
Here is my best tip. Buy a Malibu each. About. 8" to 9". Buy them second hand and sell them back to a shop when you leave. You will loose about $200 per board. Tour the east coast from Sunshine Coast Queensland. (There is no surf north of this ) to bondi beach Sydney.
Best beaches in the world.