> I take it there are some canyoning routes in Wollemi?
Funny you should mention that!
Yes, some of the world's best wet canyoning country is to be found in a narrow belt running down the W side of Wollemi. The sandstone rock there is especially hard, and the slots can be very narrow – two feet wide would be normal. You can be several abseils from the surface in places. For many canyons you need not just two full-length abseil ropes but some flotation as well, as you may be swimming for an hour or two in very cold water.
Of course, if it rains you have to get out very fast. I have seen big and small canyons go up 6' to 10' in a couple of hours. And yes, people have died in them as a result.

Sue at the junction of Crayfish Canyon and Claustral Canyon. The latter is very high grade – three longish abseils from deep water and/or into deep water. You just about need a headlamp.

This is Wollongambee canyon, which in fine weather is long but fairly easy – but it can be cold! Doing both parts will take a full day.
Cheers