The state's Environment Minister Andrew McNamara said there had been another alleged sighting of a crocodile, about seven weeks ago, at the other end of the Great Sandy Region in Baffle Creek, about 150km northwest.
Queensland wildlife officials are investigating reports of a 4.8-metre crocodile in Hervey Bay in the state's south-east.
A Victorian man, staying with a friend in the Hervey Bay marina, photographed what he said were the marks of a 4.8m-crocodile on Round Island, about 500m off the town's main harbour.
"Despite the time lapse and the distance between the events, it's still worth paying that extra bit of caution," Mr McNamara said.
Rangers said while it was difficult to confirm what made the marks, they were consistent with a crocodile.
"That's a big crocodile, so if it was still around in such a busy part of the bay, you'd expect someone to have seen it," Mr McNamara said.
"But I am still asking boaties to keep their eyes peeled and contact the Environmental Protection Agency if they see anything."