There are two types of Pike common to the southern coast of Oz - short and long finned (the short finned pike is usually referred to as a snook and are sometimes misidentified as barracuda as they are both from the same family - sphyraena). Your location states you are in Noosa, which is a bit far north for Pike (I would have thought) but is well within the barracuda zone. Barracuda typically have distinctive vertical stripe type markings on their body which your fish does not (however it looks like the fish has been scaled prior to the photo being taken which may be deceptive). Also note that Barracuda and Barracouta are two different species with the latter typically being a southern fish and having a distinctive tail and dorsal fin.
The fish's anal fin and andipose fin (the one on top behind the dorsal) look like those of a snook. Also, if you recall any vertical stripes or marks on the fish prior to scaling then it is a more likely a barracuda.
Although the photo makes it difficult to see the dorsal fin, your description (of it being fatter than you expected) and the fish's tail makes me second guess myself as those features make the fish look more like a long finned pike.
In summary, it looks like a pike in the photo, and maybe/probably a short finned one at that. Please someone correct me if they think otherwise.
I have attached some photos for comparison.