A teenager drowning at sea was saved after he used his mobile which had no phone signal to post an SOS - on Facebook..
The 18-year-old was tossed into the water when his dinghy capsized and managed to cling on long enough to reach his handset.
But he had no signal coverage to make a 999 call and with virtually no battery power left he quickly typed out the word 'STRANDED' and posted it on Facebook.
A concerned mate saw the message and rang the lad's mum who raised the alarm and triggered a massive search and rescue operation.
The teen had been treading water for two hours in the dark by the time he was spotted by a lifeboat crew and hauled out of the sea a mile off Mevagissey, Cornwall.
Jeremy Lynn from Brixham Coastguard said he was able to type a solitary word before the battery drained.
He said: "The message just said 'stranded'. One of his friends picked it up and passed it to his mother.
"It was obviously one of the last methods he had of using his mobile phone to call for help.
He is obviously a fit young lad, but was only in shorts and a t-shirt.
"The water temperatures is only around 15-16 degrees at this time of year so he would have been quite cold."
Coastguards said the boy got into trouble on a paddling trip from Mevagissey to the tiny fisherman's cove of Portmellon, a mile south.
When his boat capsized the frightened lad clung on and started trying to reach people on his phone.
Unsure whether any of his attempts had succeeded, he tried in vain to swim back to shore in just his t-shirt and shorts.
The RNLI said the teenager was "incredibly lucky" because once he left the capsized dinghy he was difficult to spot in the water.
He was taken to hospital and checked over but was not harmed by his ordeal.
A spokesman for Fowey lifeboat crew said: "Both RNLI lifeboats were taken at speed to the general area to begin a shoreline search from Portmellon towards Dodman Point.
"On the way across St Austell Bay to Portmellon the inshore lifeboat crewmembers found a young man in the water a mile from shore.
"He had capsized and, because the boat was drifting, had decided to swim for Blackhead after managing to get a message onto Facebook before his phone died.
"He was immediately transferred to the all-weather lifeboat and made comfortable while being taken to Fowey Lifeboat Station where an ambulance was waiting to assess him.
"He was wearing a t-shirt, shorts and trainers and was very cold as he had been in treading water for two hours."
His rescue on Thursday night was on a remote Cornish coast notorious for its poor 3G internet coverage and intermittent mobile phone signal.
Prime Minister David Cameron revealed only last month that he has twice cut short a holiday there because his aides couldn't reach him.