A MOTHER and her 11-year-old son were dead last night as hopes faded for her 13-year-old daughter after they were all swept out to sea.

The trio were part of a family group of five walking along Marine Drive in North Bay, Scarborough, shortly after 4pm yesterday.

North Yorkshire Police said the girl and her 11-year-old and eight-year-old brothers were playing on a slipway leading to the beach when they were struck by a large wave.

All three went into the sea and their mother plunged in to try to save them.

Her boyfriend also leapt into the water and, helped by a member of the public, who is thought to be a surfer, got the eight-year-old out safely, but by then the other two children and their mother had been swept away.

A spokesman for the Humber Coastguard said an RAF Sea King helicopter winched the mother and son out of the water within minutes, about 50 yards off the Oasis cafe slipway.

Medics fought to save the woman, who is in her early thirties, and her son as they were taken by ambulance to Scarborough District Hospital. Shortly before 8pm, the hospital confirmed that they had died.

The family is not thought to be from the Scarborough area.

Last night, the RAF, lifeboat crews and the Coastguard service were still searching for the teenage girl.

As darkness fell and with a 12ft swell in the sea, the RAF brought in a second helicopter to help with the search.

Emergency crews had initially been alerted when several people saw the incident and called for help on their mobile phones.

Michael Mulford, of the UK Search and Rescue HQ at RAF Kinloss, in Scotland, said the family had found itself in a "very, very serious" situation.

Mr Mulford said: "A helicopter from RAF Leconfield was in the area, on its way back from another call, so it was scrambled to the scene.

"The mother and her son were rescued within four or five minutes of them being in the water and were taken to Scarborough hospital, where tragically they were confirmed dead on arrival.

"The woman's partner and another man managed to get themselves out, but the 13-year-old is still missing."

He said that although the search for the teenager was continuing, hopes were fading for her survival.

"The survivability in these conditions is probably an hour at most so the chances of finding her alive are sadly very slim indeed. You never say never, but we have to be brutally realistic.

"It was very cold and there have been reports of some large waves of 12 to 13ft at that point. The conditions certainly hampered rescue efforts.

"This is a desperately sad event, an awful tragedy for this family. It has been terribly difficult also for the rescue teams. So many people gave it their best shot to rescue these poor people safely," he said.

The spokesman for Humber Coastguard said: "We received several 999 calls from people on the seafront, who saw a number of people in the water.

"A rescue operation began involving a rescue helicopter, lifeboat and Coastguard vessel. Two people were removed from the water and a search continues for a third."

Scarborough District Hospital spokeswoman Gilly Collinson said: "Sadly, both the mother and son have now been confirmed dead.

"Attempts had been made to resuscitate both whilst in the ambulances, and these attempts continued after their arrival in A&E (accident and emergency department), where we had a full emergency team on standby.

"Unfortunately, attempts to resuscitate both mother and son were unsuccessful.

"We also received in a surfer who had attempted to rescue the children, who was treated and discharged.

"Another adult man arrived by ambulance, whom we believe to be the partner of the woman who died.

"He had also entered the water, but again, we did not need to admit him. His eight-year-old son accompanied him to the hospital uninjured."

Inspector Peter Gold, of North Yorkshire Police, said: "At this stage, we don't know how the people came to be in the water.

"We need to speak to witnesses to the incident to establish what happened.

"The search is continuing for the missing child, but the longer it goes the more concerned we become."

The Coastguard spokesman confirmed that an RAF helicopter was involved in the search along with the RNLI, including the Scarborough lifeboat, police, the fire brigade, and Coastguard personnel.

Search teams were last night waiting to see if the teenager's body was washed back to shore.

Inspector Gold said: "People have been very generous in offering their help at the scene and it will be a relief when this missing girl is found.

"These have been awful and tragic events and it has been a difficult time for everyone involved in the search and rescue efforts."

* The father and his eight-year-old son were last night being cared for by specially trained police officers.