Two men safe after boat capsize off Sydney

Two men are being treated for hypothermia after being rescued from their upturned boat off Sydney's southern coast.

After an emergency radio beacon was activated on Saturday night the boat was spotted by an ambulance helicopter crew about a nautical mile off Cronulla with two men, aged 36 and 28, sitting on the upturned hull.

The men, who were not wearing lifejackets, were taken to Sutherland Hospital to be treated for hypothermia, with one also treated for cuts to his head.

One of the men had swum under the upturned boat to retrieve the emergency beacon, police said.