As soon as the weather gets warmer in Canberra we head to Kambah Pools for a swim.  It's a wonderful place to spend an afternoon as it's quiet and tranquil and the natural bush setting makes it very peaceful.  When it's busy it's often possible to walk further along the river and find a spot by yourself if that's what you're after.  Be warned though, parts of the river are designated as 'clothing optional' which means there are places that are nude friendly which is often good to know before you wander in with the kids and grandparents!  However the majority of the river is family friendly.