Is it a sunken treasure? Nope, it’s likely the mysterious chassis of an old truck lurking in the waters off Bribie – well, that’s the best guess so far, anyway.

Late last year the Caloundra Coastguard team put out the call to local super sleuths after the metal shell of an old structure was exposed on the ocean side of Lions Park (opposite Military Jetty) in the surf break.

Caloundra-based photographers Bluey’s Photography and Benjamin Sands snapped some shots of the structure (pictured) and locals began their quest to figure out why it was there and what it is.

Caloundra Coastguard Flotilla Commander Roger Pearce said the initial guess was a landing barge, but the idea was soon shot down as the structure was sized up as being only 3m x 4m.

“There were landing barges there in the Second World War period which they used to come off a bigger ship and land troops on the beach,” Mr Pearce said.

“There was discussion about that being the case but then someone ruled that out due to its small size.”

Other guesses included a target barge for gunnery practice during the war, a barge from Military Jetty and a boat float frame.

But Local historian John Groves believes he cracked the case, along with the help of Caloundra stalwart Les Clarke.

“We believe it’s a car body chassis from around the 1950s,” Mr Groves said.

“They used to do net fishing over at Bribie and had trucks over there.

“Les Clarke remembers his father, who set up the Ice Factory in Majola Avenue, told him there was a truck rollover there and this is believed to be the upside-down chassis.

“We are not sure what type of truck, but you can see where the winch went through to pull the nets in – it looks to have been buried all this time with the part still buried intact.”