We passed 9,000kms as we ventured north of Cairns to the oldest rainforest in the world, the Daintree Rainforest. It looked much like any other to our untrained eyes though (and despite an audio guide at a Discovery Centre) but we did see some lovely blue butterflies and had a great swim in a river whilst messing around on some submerged rocks.
We also went to Cape Tribulation "where the rainforest meets the sea". The beach was pretty much deserted and quite nice but the water was something special. You get used to warm seas round here but we've never known such warm water. It must have been low 30s (high 80s in old money), it really was luke warm like the dregs of a nice cup of tea. Unfortunately though you can't swim in tropical waters at this time of year without a rather fetching stinger suit* or some nets (although some people did) due to the box jellies and other nasties, so we only dipped our toes and read a bit.
*see the new photo from our Whitsunday sailing!