Authorities are gravely concerned about the welfare of 80-year-old Swiss yachtsman Peter Baggenstos who was last seen in Hobart nearly two months ago.
The Swiss national set sail for New Zealand on his 13-metre yacht "Lady Lay" on December 1.
The yacht's transponder stopping transmitting on December 5 about 140km off Tasmania's east coast, which at the time was understood to have poor weather.
The Australian Maritime Safety Authority conducted large-scale search operations in the Tasman Sea but neither Mr Baggenstos or the yacht were found.
He was in good health and considered a strong sailor.
The vessel was fitted with safety equipment including a life raft, distress beacon and GPS unit.
The investigation has involved AMSA, interstate, international law enforcement agencies and Interpol.
Tasmanian police have now taken over the investigation and hold grave concerns for his welfare.
New Zealand authorities have no record of Mr Baggenstos arriving.