Police are investigating after a 98-year-old paddle wheeler sunk in the Thomson River at Longreach, just weeks out from the start of peak tourist season.
Tourism operator Outback Pioneers said the Pride of the Murray was moored in the river awaiting the start of tourist season at the end of the month.
The company said it learned from police early today that the boat had sunk.
Longreach Major Organised Crime Squad Rural officer Allan Cook said police were notified by a kayaker that the boat was sinking shortly after 7.15am.
He said it was unclear why the boat sank, but his squad was investigating.
"[The kayaker] observed the Pride of the Murray was a little low in the water, they didn't think too much of it at that point in time but when they came back about half an hour later, they saw the vessel list to port and capsize on its side," he said.
Officers said they were treating the incident as suspicious until proven otherwise.
"There would be no circumstance that we would be looking at that would suggest this would be a natural event, so we have to treat it as suspicious," Detective Sergeant Cook said.
Owners in shock
The 100-tonne boat, which was trucked 2,300 kilometres across the outback from country Victoria to western Queensland last year, was completely submerged in the river.
Outback Pioneers founder Richard Kinnon said the sinking was a shock but he hoped the boat could be retrieved.
"We will do whatever is necessary to ensure our guests still have a fantastic cruise experience in Longreach," Mr Kinnon said.
"This is a setback but not the end of the story."
The company said it would contact tourists who had already booked tours on the boat, and its other vessels were still operating.
Concerns over water supply
The Thomson River supplies water to the town of Longreach, which has a population of about 3,000 people.
Mayor Tony Rayner said the council's highest priority was ensuring the supply wasn't contaminated by leaking diesel from the vessel.
"Fortunately there's only a very small amount of diesel in that vessel, and a small amount of oil," Mr Rayner said.
He said at this stage, there was no risk to the town's water supply.
The Pride of the Murray has a 600 litre fuel capacity, but authorities said it was unclear how much diesel it contained when it sank.
Cr Rayner said spillage flotation devices were expected to arrive on Monday afternoon and would be used to capture and contain any leaking diesel.
But he said windy weather would help push the contaminated water to the shore, slowing its spread.
"We'll also work with the environmental agencies to mop up any diesel that is there," Cr Rayner said.
Retrieval operation
Detective Sergeant Cook said a salvage experts would help restrain and then retrieve the boat, which was expected to take a week.
He said the maritime authority would take over the investigation but police would bring the boat to the surface.
"And then we can commence our investigation from a work, safe and health perspective," he said.
He said police were working with nearby properties to access CCTV to get a better understanding of what happened.
"But at this stage, the jetty and the vicinity is subject to the crime scene," he said.
Cr Rayner said his thoughts were with Mr Kinnon.
"Knowing Richard and Maurice Kinnon … they'll regroup and regather very quickly and do their best to get the Pride of the Murray up and running," he said.
"But obviously that will take many months before that happens."
