i studied abroad in sydney a few years back. go to that site mentioned by manda, and also check with the local univiersities for waterksi/wakeboard clubs. australia has tons of great places to ride,with really dramatic scenery.
But....you'll be in Brisbane, go surfing!!!!! wakeboarding is slower to pick up in australia b/c the surfing is amazing and very accesible. i love wakeboarding, but...when in rome.....