Police say a wreck found on the seabed near the entrance to Picton Harbour could be that of a fishing boat at least 40 years old.
The vessel on the sea floor was spotted during a naval exercise and images were passed to the police on Wednesday.
Following a second inspection by divers, the police now believe it could be the Black Prince, which operated as a fishing boat in the 1970s and was converted into a pleasure craft in the 1980s.
Senior Sergeant Peter Payne said they would like to talk to anyone who had knowledge or photographs of the Black Prince.
He said it was also known as the 'Blue Submarine' because of the way it moved through the water.