If you reckon you've had enough flat water on LBG maybe Longreef if you're north side. I've never sailed there. I'd have thought you'd sail north of the reef? It looks like this is taken south of it?
Or if you're Sydney south side and looking to launch behind a bit of a protecting reef maybe Bulli is the closest? The first 400 metres heading east is somewhat like LBG, beyond that you're in the ocean. Which takes a bit of getting used to for a Canberran, but it's worth it.