The 19-foot boat overturned in Great Oyster Bay about 4.30pm and an EPIRB signal was detected by the Australian Maritime Search and Rescue Coordination Centre in Canberra.

The Westpac police rescue helicopter, a coast guard unit and local fishing boats were assigned to search for the overturned vessel, which was located about 90 minutes after it capsized.

The three men from Hobart’s eastern suburbs were treated for mild hypothermia by members of the Tasmania Ambulance Service at Little Swanport.

A police spokesman said it was believed the boat had been swamped by waves after a fishing line became entangled around the propeller.

All three survivors were wearing Australian standard life-jackets.

The police spokesman said the men had broadcast a mayday message on their VHF radio prior to the boat sinking and had also activated their EPIRB appropriately.

Tasmania Police Sergeant Charles Stingel said the signal -- from a new digital EPIRB -- identified the position of the vessel, along with a description of the boat and the name of its owner, which made ``rescue coordination far easier.''

Last February, older 121.5MHz EPIRBs were made obsolete with the introduction of the newer 406MHz satellite frequency.

``Thankfully, the people involved in this incident were not injured,'' Sergeant Stingel said.

``Their boat sank very quickly in calm conditions, but all were wearing inflatable life jackets, had the required safety gear and -- importantly -- knew how to use it.

``It is reassuring that they were located at the exact coordinates originally transmitted by their EPIRB.''

``I would also like to acknowledge the assistance provided by the boating community in general, who never fail to drop everything and assist in these situations.''

The vessel overturned at Great Oyster Bay near Swansea on the state's east coast...