The children's father leapt into the water and swam out to get to them but was overcome by the waves.

While onlookers on the beach made desperate 999 calls to the coastguard, a jet-skier is understood to have waded in and hauled the family to land.

The dad (39), his daughter (eight) and son (12) were taken to Lynn's Queen Elizabeth Hospital by ambulance and discharged after one night.

Lifeboat press officer Geoff Needham said they had a lucky escape and has renewed warnings over the deadly potential of using inflatables in the sea.

The incident was the third of its kind attended by Hunstanton lifeboat in as many days.

Mr Needham said: "These things are lethal. We would not advocate their use in tidal waters, but if people do use them, they should be tethered at all times and an adult should be present.

"What seems an idyllic situation can turn very nasty in a very short space of time once the wind and tide catches.

"These are avoidable incidents if people were to be more responsible."

The family, from Cambridge, got into trouble close to Hunstanton lighthouse just before 4pm on Tuesday.

Lifeboat crews administered first aid before handing over to paramedics. An air ambulance was called but re-diverted before its arrival.

A ten-year-boy and his father were rescued by a swimmer as they started to drift out to sea on an inflatable dinghy off Heacham at 1.20pm the same day.

A kayaker saved a group of teenagers drifting off Brancaster in a dinghy on Saturday, as reported in the Lynn News.