Horrified onlookers saw the youngster jump out of the rubber inflatable and disappear under the water.

The alarm was raised by the boy's father and coastguards and a police helicopter raced to the beach at Saundersfoot, near Tenby, Pembrokeshire.

The boy was given emergency treatment by a doctor and paramedics on the beach and then airlifted to Withybush Hospital in Haverfordwest.

Coastguards at Milford Haven said the alarm was raised at about 1140 BST on Saturday when they were told the youngster had drifted out a "few hundred yards".

The Tenby inshore lifeboat was dispatched to the beach and as well as police crews and the Dyfed-Powys Police helicopter and the rescue helicopter from RAF Chivenor in Devon.

Ten minutes in water

A coastguard spokesman said: "Apparently the father had swum out to try and rescue the child who somehow had drifted away from him.

"But he failed to reach him, and at some point he saw the child jump into the water."

The lifeboat crew found the boy, who had been in the water for about ten minutes, and brought him to the shore where his parents were waiting.

He was formally pronounced dead at 1300 BST.

Coastguard advice

Fiona Warren, spokeswoman for the Maritime and Coastguard Agency, said the boy's family were from the Herefordshire area, and had been on holiday in Saundersfoot.

She said: "It was a tragic and unfortunate accident."

The agency has repeated its advice for people to always tie inflatables to the shore.

Winds in the area are said to have been northerly, force two to three, at the time of the incident.