Three teenagers thought they were going to die when an after-school dip in the sea turned to terror.

Friends Belle Peck, 14, and Chloe Bennett, 15, were on a sand bank when the tide swept them off into deep water at The Leas at Minster in Sheppey.

Their pal Billy Kerswell, 16, raced into the sea to rescue them but the effort left him gasping for breath and floating face-down in the water.

Belle then struggled back into the water to pull him to safety before all three collapsed on the beach.

The drama happened at the end of one of the hottest days of the year and led to calls for a major safety campaign for schools in Sheppey and across Kent.

All three youngsters, who attend the Island's Oasis Academy, needed oxygen from the crew of the Sheerness inshore lifeboat before being taken to A&E at Medway Maritime Hospital.

Doctors feared the three were in danger of suffering from "secondary drowning" – where the body's internal organs cannot cope with the amounts of salt water swallowed.

Belle, from Kingsborough Manor, Eastchurch, fought back tears as she said: “We all thought we were going to die. It was terrifying.

"If Billy hadn’t dived in to rescue us we wouldn’t be here now.”

Her mother Laura, who said her daughter loves swimming, said: “They all helped each other and got out of the water.”

Neither Billy, of New Road, Minster, nor Chloe, of Clover Close, Minster, wanted to talk about their ordeal.

All three were released after treatment but Billy was taken back into hospital the following day after collapsing. He is now back home.

Belle said: “It was hot so Chloe and I went for a swim in our clothes.

"We had been having fun in the sea and were wading in the water on the sand bank when the sand suddenly dropped away and the waves were smashing into our faces.

"We were out by the buoys.

“It seemed like we were swimming for ages but we weren’t getting anywhere and were really exhausted.”

After screaming for help, Billy swam out from the shore, put Belle on his back and pushed Chloe in front. Belle described him as a hero.

"We were wading in the water on the sand bank when the sand suddenly dropped away and the waves were smashing into our faces" - Belle Peck

She said: “When our feet touched the ground it was an amazing feeling.

"I staggered to the shore then looked back and saw Billy floating head-down in the sea.

"I don’t know where I got the strength from but I waded back in and tried to pull him out.

"It was terrible. His face had gone green.”

Chloe had collapsed on the beach and was shivering from the cold.

"By this time her mother had arrived and was trying to keep the youngsters warm with blankets. Belle suffered a panic attack and was hyperventilating.

She said later: “We all just kept hugging each other.”

The RNLI has offered to take the youngsters back to the beach to explain when and where it is safe to swim.

In a sinister twist, the parents became the victims of internet “trolls” who accused them of not looking after their children.

Chloe’s mum, Mary Sheehan, said: "This is what teenagers do when they live on an island.

"They go to the beach and have a swim. But I don’t believe many youngsters are aware of the dangers. This could have happened to anyone.

“The full shock of what happened is just sinking in.

“We are all so relieved they are still here.

"This is what happened when those men died at Camber Sands last year. It could have easily ended in a real tragedy.”

Billy’s mum, Michelle Clements, said: “Billy was celebrating finishing school and had just passed his sports exam.

“He is naturally sporty, and a strong swimmer, but this rescue really took its toll on him.”

Meanwhile, RNLI lifeguards are planning to ramp up their beach safety campaign after the latest Sheppey drowning scare.

They have already visited 16 Island primary schools with their Meet the Lifeguards roadshow, but there is now talk of including Oasis Academy students.

The scare comes as this week an inquest was opened into the deaths of five young men who tragically drowned at Camber Sands in Sussex after getting into difficulties, with the hearing told the beach has hidden dangers.

With many more families moving to Sheppey, RNLI bosses admit they are concerned newcomers are not aware of the dangers of swimming in the sea and the precautions needed.

Swale council said its contract with the RNLI provides lifeguards at Minster for the peak summer season, July 8 to September 3, based on predictions for beach use.

Neil Withers, the RNLI’s Sheppey lifesaving manager, said: “We are investigating how best to engage with the community to improve water safety for those living here and visitors.

“Our team has visited a large number of schools although we were surprised by the number of children who said they couldn't swim.”

He also hopes to recruit more lifeguards from Sheppey.

Swale council’s seafront officer, Ian Arnell, said: “I personally would love to see water safety, swimming and first aid taught as part of the National Curriculum, but that is down to government policy.”

Oasis Academy principal John Cavadino said: "We are aware of this incident involving our students, and their welfare is our prime concern."

A Swale council spokesman said signs and information are provided.

• For safety information visit https://rnli.org