The heroic bystander entered the water three separate times despite the harsh conditions out at sea

A heroic bystander risked his own life to rescue two children from the sea during a tragic incident in Essex that claimed the lives of a mother and her teenage daughter.

The tragedy at West Mersea, near Colchester, on Wednesday evening saw 41-year-old Shally Rahman and her 15-year-old daughter, Samiha Rahman, enter the water in an attempt to rescue a seven-year-old boy who had become stranded.

Both were pulled from the sea after getting into difficulty, but sadly died.

According to Essex Police, the victims and the young boy, who remains in hospital in a critical condition, were all members of the same family from Barking, east London.

Three other people were taken to hospital after the incident.

Witnesses have praised the actions of an unnamed man who repeatedly swam into the sea in an effort to save those in danger.

Beverly Smit, 60, described the dramatic rescue, saying the man entered the water three separate times despite the harsh conditions out at sea.

She said: "They were calling for help and the children and adults were out there. He swam out, I think, three times. Two of the children he brought back were not in good condition."

Many members of the public rushed to assist before emergency crews arrived.

Staff from the nearby Seaview Beach Diner, including teenage employees, joined other bystanders in trying to help.

Leonie Powling, 19, who was working at the café, recalled seeing CPR being administered to those pulled from the water.

"We wished we helped a bit more, but we did what we could," she said.

"Now knowing that people have died, it's a lot sadder that we were there and kind of witnessed it."

Residents living nearby also responded, bringing blankets to support survivors and assist emergency personnel dealing with the aftermath.

Speaking from Bangladesh, Shally Rahman's brother-in-law, Matiur Rahman, said relatives were struggling to come to terms with the tragedy.

"We are very shocked. We can't explain what has happened," he said, describing Samiha as "a very, very good person" and Shally as "a very helpful person."

The young boy is said to have become stranded on a sandbank after being cut off by the incoming tide, prompting family members to enter the water in an attempt to rescue him.

Essex Police have launched an investigation into the circumstances of the incident.

Detective Chief Inspector Al Pitcher said officers are interviewing dozens of witnesses as they work to establish the full sequence of events and have appealed for anyone with information to come forward.