A mystery yacht found on the sea floor of the Picton Harbour could be the Sioux - an uninsured $150,000 vessel which went missing five years ago.
Police said the wreck was about 10m long and had been found near the entrance to the harbour on Friday during a Defence Force training exercise.
Acting area commander Senior Sergeant Peter Payne said it fit with the disappearance of the Sioux, a 10m vessel which broke free from its mooring in Waikawa Bay during stormy weather in June 2010.
Shortly after the vessel's disappearance, yacht rigging was reported in the water near where the wreck has been found, but police were unable to locate the rigging at the time.
Police divers would investigate the wreck and confirm the identity of the vessel as soon as arrangements were made, Mr Payne said.
He said there were no other boats than the Sioux known to be missing in the Queen Charlotte Sound and police had been in contact with its owner, Paul Sugrue, who offered a $5000 reward for information leading to the yacht's recovery in 2010.
It is understood the newly-found wreck has been underwater for about five to 10 years.
Police would not be drawn on whether the wreck could be connected with the high-profile disappearance of Olivia Hope and Ben Smart in 1998.
Tasman District police communications manager Barbara Dunn said she could not comment.
"We wouldn't even speculate on anything like that," she said.
Witnesses to the last sighting of Ben Smart and Olivia Hope gave descriptions of them boarding a "distinctive class ketch, with two masts, about 12-13m, with a white and blue hull with round portholes".
A boat matching the description was never found by police.
Scott Watson was convicted for the murders of Smart and Hope and is currently serving a life sentence.
Previously, a deliberately-sunk yacht found in Gisborne Harbour in 2000, was linked to the pair's disappearance by those who believe Watson is innocent of their murders.