Its a bit of a cop out But at least, unlike the Type 42 RAN Light Destroyer, RAN FAA Hellcat, or RAN Flight 1 Arleigh Burke, is actually finished.
Australia's independent nuclear deterrent had been built concurrently with that of the United Kingdom, adopting common launch platforms to those used by the UK with the RAAF being responsible for Australia's deterrent. This worked well until various defence reviews in both the UK and US made the RAAFs retention of the role difficult, however, even though there was a very clear need for more tactical, as opposed to strategic air power in light of the changing regional strategic environment, the RAAF retained the deterrent where the UK migrated to Polaris. The cancelled Blue Streak and Skybolt projects saw the B-58 acquired to replace Vulcan and later supplemented with FB-111A, using WE.177 bombs while the B-1A was planned as the as the next generation.
The reason Australia had not acquired polaris was two fold, first the US was reluctant to provide the System to Australia and secondly there was great reluctance to take the mission from the RAAF let alone let the RAN get into nuclear propulsion. Ironically it was the first Australian Labor government in twenty three years that launched a defence review that resulted the transfer of the deterrent mission to the RAN leading Australia to lobby the US for Trident and six modified Ohio Class SSBNs.
Of course once the B-1B project is kicked off, Australia had a new government and orders of 24+12 of a modified version capable of conventional missions, cutting the Ohio order to four, another change of government saw the cancelled subs reinstated and delivered later in the mid 1990s
This model is of the lead ship of the second batch of two boats, HMAS Victoria. The primary external difference is a re-profiled lower forward fin base scalloped to improve hydrodynamic flow.