The family was on holiday when the woman, named as Rosemary Wickstead from London, got into trouble at Borve on the Isle of Harris on Monday evening, swimming in an area known for strong currents, in windy conditions made worse by the firm Atlantic swell.
She had been recovered from the sea at Traigh Mhor by the time coastguards and a local doctor arrived.
They tried to revive her before she was airlifted about 50 miles to the Western Isles Hospital at Stornoway on neighbouring Lewis.
The alarm had been raised at 7:40pm when Stornoway Coastguard received a 999 call from a resident on the west coast of South Harris reporting that a family had got into difficulty swimming from Traigh Mhor near Scarista – often named as one of the best beaches in the world.
The beach, below Borve Cemetery, looks out towards part of the uninhabited island of Taransay, the setting of the BBC series Castaway 2000.
Tarbert Coastguard Rescue Team, which had been out training, was sent to the beach.
Team members found Mrs Wickstead already recovered from the water but unconscious and started resuscitation attempts. A local doctor is also believed to have attended.
Her husband and children were transferred to hospital by road ambulance, said coastguards.
It is believed their treatment was merely precautionary because they too had been in the water – they had not suffered major injuries.
However, the woman was pronounced dead at the hospital.
“A woman was flown to the Western Isles Hospital by HM Coastguard where she sadly died,” said a spokesman for Police Scotland.
A report will be made to the procurator fiscal.
Police confirmed that the family were from the UK but not from the islands. A coastguard spokesman said people needed to be well prepared for the local swimming conditions.
He said: “Even at this time of year the water is between 9C and 11C and you will get cold very quickly if you are not properly prepared.
“We do not know exactly what happened in this case –
inquiries are continuing with the police.”
One local resident said yesterday: “That beach is renowned for strong currents. It shelves and last night there was a bit of a swell and it was dull and windy. It is a beach that locals tend to avoid for swimming, but it is very picturesque.”
Harris councillor Catherine Macdonald added: “The beaches of the west of Harris are beautiful and are renowned the world over.
“They are popular with swimmers but some have strong currents and people need to be careful about where they swim.
“The beaches are so attractive it may not always be apparent that there are dangers. People have been attracted to them –
especially with the recent weather we have been having.”