Nice diving spot, which you can dive with AirBuddy: a small, light-weight portable dive equipment, which brings the ease of snorkeling into the fascinating world of diving. www.airbuddy.com
Pretty beautiful (and seemingly popular) diving location. The left side is harder to get to (you have to chamber down some rocks) but imo was a nicer and slightly deeper dive.
Tour of the island is only available on Sundays. If there is no tour, the gate to the fort is closed. Check NSW National Parks and Wildlife Service website for details.