Pufferfishes, Porcupinefishes, Boxfishes and Triggerfishes are all in the order Tetraodontiformes. This web page focuses on the family of Leatherjackets (Family Monacanthidae) which are well represented in Sydney and common on every dive. This is a diverse group with plenty of colour and many shapes and sizes, all with very similar defining features such as prickly scales, a prominent first dorsal fin spine that is either in its upright position or down, as the fish likes. They have small mouths often with visible large teeth.
In nearly all species the spine can be either folded back or put in the upright position. In a few species they can extend their chest area outwards, for example the Fan Belly Leatherjacket. I have seen male Pygmy Leatherjackets do this during a mating dance, in an attempt to impress the female.
Black Reef Leatherjacket (Eubalichthys Bucephalus)