Yeah, there is not a lot of fresh water.
Believe it or not, Coomaditchy Lagoon has fish...I know because I have caught fish there Little to no over hangs, so might be good for fly fishing...Just don't eat any of them. The tip is on the other side. So the water is probably not the best.
Kangaroo Valley is worth a try. Don't take the Berry turn off...go through to Nowra. At the first roundabout at Bomaderry turn right and just follow that road and you will get to Kangaroo Valley. Ask any shop owner or local to point you towards Bendella.
There are some smaller creeks around Jamberoo. Go via Albion Park not Kiama.
Along the Illawarra Hwy heading towards the hills, on your right is Macquarie Rivulet. It is all private farm land, but most of the owners will be happy for you to fish there. You just might have to walk a bit to find the holes....Oh, and knock on the door and ask the owner first
Back south...The Shoalhaven River becomes fresh at a bit east of Burrier. At Burrier it is considered "brackish" but really, I have never tasted salt there. Burrier also has a caravan park with boat ramp. There is another caravan park further on (which is better). Just treat the give way and stop signs with respect.
There are plenty of spots on top of the hill. Bowral, Moss Vale etc...but not this time of year unless you like ice...
itsaboat mate...Life is just a boat and then ya marry one !