North Australian FISH FINDER forums

https://www.news.com.au/travel/travel-u ... cdc2b3ade5

Gladstone's Boyne River is the usual southern limit, but crocodiles have been confirmed southwards at Agnes Water, Mary River, Burnett River, Coonarr Beach and Inskip Point.

I'm willing to believe that a croc could make it's way down there but based on those screen settings there's no way that the sidescan is of a big crocodile