Ok so I've teased this long enough. This is a gravid female Port Jackson Shark - Heterodontus portusjacksonii - a member of the family called horn sharks (I'm going to try and keep the innuendos to the minimum) and she is to quote her fellow Australian, the late Steve Irwin, a goregous sheila.
In all seriousness the sharks above are a mix of male and female but mostly female. When I arrived in Jervis Bay, NSW where these were taken I couldn't dive for the first 2 days. A walk on the beach revealed a lot of Port Jackson eggs washed up by the storms. When I got into the water on dive 1 I found these huge aggregations of spawning or post-spawning sharks everywhere (sharks can be sexed by the males external claspers and the females were all massively fat or stick thin). In all I saw about 3-400 of these chaps (they're hard to keep count of) over the dives and 3 other species of sedentary sharks. It was awesome but like so many other things simply due to being in the right place at the right time.