At least three saltwater crocodiles inhabit the area under the Captain Cook Highway bridge over the river, about 7km south of Port Douglas.
The reptiles, which occasionally bask next to each other, are regularly snapped by passers-by.
Hartleys Crocodile Adventures wildlife manager Drew Melville said the trio of predators may be too small to take a person.
But, he said, that did not rule out a much larger croc stalking the area.
"I would not recommend anyone go swimming in the Mowbray River or its tributaries," he said.
"There's the possibility that there is a large male croc in the there and no one has seen him.
"So you've got Dickson Inlet, where there is definitely one over 4m plus.
"And of course, even rivers like the Daintree or Coopers Creek are well within the travelling range of larger crocs."
Department of Environment and Heritage Protection rangers were last night surveying the Mowbray River and tributaries for any signs of a large crocodile that may have taken Anne Cameron.
Crocodiles that have previously attacked people are known to display aggressive and territorial behaviour.
There were several sightings of crocs in the Mowbray reported to EHP.
However, as the river is well within crocodile territory, only warning signs were erected alongside the permanent warning signs at the bridge that have been in place for some time.
Mr Melville said swimming in creeks anywhere between Rockhampton to the tip of Cape York was definitely not advisable.
"And that would be a tragedy, indeed, if this is what has happened (with the elderly woman)," he said.
The suspected fatal attack follows the death of Cairns spearfisherman Warren Hughes, 35, who was taken by a crocodile near the mouth of the Russell River in March.
FNQ AUTHORITY IDEA REJECTED
THE Palaszczuk government will not support basing a Queensland Crocodile Authority in Cairns.
Bureaucrats from the Department of Environment and Heritage Protection fronted a public hearing in Brisbane on Wednesday to discuss Katter's Australian Party's draft legislation, the Safer Waterways Bill. One component of the Bill includes the creation of a crocodile authority, based in Cairns, which would be tasked with issuing permits for legal crocodile egg harvesting in Queensland and to landholders to manage crocodiles on their own land.
But the EHP officials, in their official submission to the inquiry examining the Bill, want the requirement for public servants employed by the authority to live and work in Cairns to be removed.
The department's Dr Beth Clouston said having staff based in Cairns would limit officers' capacity to respond to croc sightings in a timely and efficient manner.
EHP also says there may be "industrial relations implications" relating to forcing staff to live and work in Cairns.
