Rudie Kuiter "Guide To Sea Fishes of Australia", pages 66-67 say this is probably a smooth flutemouth (Fistulari commersonii), as it was seen in shallow waters. Neville Coleman "Australia Sea Fishes South of 30 degrees S", page 82, says it is a Smooth Cornetfish, also Fistulari commersonii.
I could only make out one set of fins on the tail section, but my photo isn't that good. https://www.whatsthatfish.com/fish/cornetfish/414#24 gives some good examples, including the shape of the fish as it moves.
On the basis of probability, most likely F commersonii, although not impossible that it could be F petimba. I have many photos and records of the former, and none confirmed of the latter. Need a super detailed hi res photo (a panorama perhaps? - not going to happen!) to get enough detail to ID this species. Its shape precludes ID from a normal single pic.