Queensland rangers have confirmed an animal snout filmed and photographed breaking the water's surface near Dunwich on North Stradbroke Island, also known as Minjerribah, belonged to a gentle dugong rather than a predatory marine reptile.
Some locals who posted pictures were convinced the plant-eating sea cow was "definitely" the crocodile spotted about 4km north on Wednesday by a local Quandamooka man while he was leading a kayak tour.
"Rangers and wildlife officers have reviewed footage taken this morning and have confirmed it shows a dugong in shallow waters on the eastern side of the island," a Department of Environmental and Science spokesperson said in a statement on Friday.
Rangers are still searching on boats and with drones for signs of a crocodile around the island, which would be more than 400km south of its usual habitat range.
They have warned people and their pets to stay away from the water's edge on the eastern side of the island.
"Visitors and residents on Minjerribah are asked to stay away from beaches between Amity Point and Dunwich while the investigation continues," the department spokesperson said.
"Members of the public are asked not to launch private drones on and around the island until further notice."
If a crocodile is found it will be in what's classified as an atypical habitat zone and removed from the wild under the state government's management plan.
Quandamooka man Mark Jones first reported the crocodile after seeing it while leading a kayak tour on Wednesday morning and other holidaymakers had also seen the creature in recent days.
Saltwater crocodiles are not endemic to Queensland's heavily-populated south with their most southerly verified range ending at Hervey Bay.
The last confirmed crocodile in the wild southeast was a 3.83m animal, which was shot dead by locals at Logan Village on the Logan River in 1905.
There have also been earlier sightings further south at Nerang and Angourie and Lismore in NSW, but only the latter was verified and she was an escapee from a travelling show named Hector, rather than a natural migrant.
Experts believe the crocodile on Minjerribah has either been released by a local private owner, although that's highly unlikely, or it could have drifted on ocean currents.
Crocodiles can travel large distances at sea, particularly after floods, and ocean temperatures have topped 26C in recent days in southeast Queensland.
There were 41 crocodile attacks on humans, 12 of them fatal, in Queensland between 1985 and 2021.
10°C