UPDATE: A UNIVERSITY of Queensland professor says it is "entirely possible" a salt water crocodile is lurking in the upper reaches of the Mary River, at Gympie.
A Gympie father and son have told how they watched a 2.5m croc for some time on Wednesday when they went fishing near the weir at Kidd Bridge.
UQ Professor Craig Franklin said salt water crocodiles could swim hundreds of kilometres and that it would not be surprising if the beast had travelled down from the Fitzroy River near Rockhampton.
"They have been found further south than the Mary River," Professor Franklin said.
"It would definitely be a salt water croc."
An expert in reptile evolution, Professor Franklin said if the reports were accurate, a 2.5 metre animal would be classed on the smaller end of the size spectrum.
"We have caught them up to five metres in river systems," Professor Franklin said.
"People need to be aware that they are there," he said.
WHEN the opportunity arises, Gympie man Scott Barton and his stepson Harley Clarke pack their fishing gear and head to the Mary River weir near Kidd Bridge, hoping to jag a catch.
Late on Wednesday afternoon as the two made their way down to the river bank, two young girls, who Mr Barton described as "in a panic" told him their dog had almost been taken by a crocodile.
Not thinking too much of it, Mr Barton says he continued down to the weir.
He was determined to get some fishing in.
However, his scepticism soon turned to disbelief when he saw a "six to eight foot crocodile," (2.5m) stealthily swimming in the middle of the river about 100 metres upstream of the weir, between the popular swimming and fishing spot and the other popular swimming and fishing spot the reopened to the public yesterday, The Sands.
"We were watching this croc swim backwards and forwards," Mr Barton said. He was deadly serious.
"There was three other people with us just watching it swim. You could see the length of him. The moment you made a noise he would just sink. We all saw it."
An experienced angler, Mr Barton said there was no way he could have mistaken the creature for anything else.
While crocodile sightings in the Mary River are not uncommon, there has never been a documented, officially confirmed sighting in Gympie.
They are usually restricted to much further downstream, closer to Maryborough.
Mr Barton is concerned for the safety of Gympie's river users, particularly over the holiday period.
"Just be wary," he warned.
"The ducks were just flying away from (the crocodile) as he swam towards them. It was definitely a six foot croc.
"We go swimming in the river every couple of weeks, we will be going to a pool now," Mr Barton said.
The last officially reported Mary River crocodile was in September this year, near River Heads.
Information on crocodile sightings can be found on the Queensland Government's Department of Environment and Heritage Protection website.