News that the historic paddlewheeler Pride of the Murray was sinking was passed on to police at Longreach by a kayaker out on the Thomson River on Monday morning.
The paddlewheeler, the newest attraction for Longreach tourism group Outback Pioneers, sank at its mooring on the Thomson River at around 7am.
According to senior sergeant Chris Smith, the kayaker saw that the boat was low in the water the first time they paddled past and then that it had capsized to one side on the return journey.
"There's no indication that anyone was on board," he said. "At about a quarter past 7, it had sunk for reasons unknown at this stage."
All that could be seen by mid-morning was the boat's roof.
Longreach police are working with Maritime Safety Queensland and the Australian Maritime Safety Authority to investigate the cause, and Sgt Smith said the owners had arranged for a salvage company to look at the boat on Tuesday.
In the meantime, the area is being treated as a crime scene until a cause can be established.
Sgt Smith said that together with the local SES and community volunteers, weighted buoys were being put down around the boat, partly to contain the diesel that would be entering the water, and police would be guarding the site 24/7 until investigations had been concluded.
After the 100-year-old vessel concluded its epic road journey from Echuca last year, nearly 30 boat specialists in Longreach worked to make it cruise-ready, including re-corking and tarring the entire giant hull by hand using a 2000-year-old boat technique still used today.
"The Pride of the Murray now looks as good as the day she was first launched," Mr Kinnon said at the time.
"She has undergone full safety checks; the paint has been touched up and she's had a clean and polish throughout.
"The team has worked from dawn to dusk and in 10 days it ensured the Pride of the Murray was ship-shape to welcome her first passengers."
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