The teenage girl and woman who died after getting into difficulty in the waters off an Essex beach have been named .

Family members identified the pair as Shalina Rahman, a 42-year-old British-Bangladeshi teacher who is married to a Bangladeshi politician, and her 15-year-old daughter, Sameeha. A seven-year-old family member was also said to be on life support in a hospital in London after the incident.

Shalina Rahman’s husband is Mansur Rahman, the leader of Jubo Dal UK, the overseas youth wing of the Bangladesh Nationalist party in Britain. Her father is Mujibur Rahman, the former vice-president of the party in Britain.

The family are understood to have been on a summer holiday trip in West Mersea, where they may have got into difficulty after a heavy incoming tide caused the sand beneath their feet to give way, sweeping them into the water.

Essex police was called by the ambulance service at 5.35pm on Wednesday after reports of the incident near Seaview Avenue in West Mersea.

DCI Al Pitcher said: “Our thoughts remain with the family members who are coming to terms with their loss. We are grateful to the people who have already spoken to us and helped with our inquiries. We would ask anyone who was at the beach at the time, and who has not yet spoken with officers, to please get in touch, to help us understand what happened.”

Emergency services urged people to avoid part of the beach in Essex on Wednesday night after what the coastguard rescue team described as a “tragic incident”. The beach reopened on Thursday.

Family friend Mishba Uddin said he believed the seven-year-old girl had got into trouble in the water and Sameeha, her older cousin, then tried to help. Uddin said that as far as he knew the mother and teenage girl who died “were not very good swimmers”.

He said that those involved came from east London, with one family based in Barking. Carl Powling, a councillor for Colchester council, said his daughter was one of three teenage waitresses at a local cafe who tried to help. “Members of the public witnessed it, called the emergency services, helped starting to pull people out, then they went into the Seaview caff to ask for assistance,” he said.

A woman, who did not give her name, told the Press Association the incident happened at high tide, which caught the small group on a sandbank.

“It comes in very quickly and you have to be careful,” she said, adding that there was “quite a commotion” and “just total panic”. She said helicopters were deployed and the air was filled with the sound of sirens.

“That was quite alarming, for a small place like this, I think that’s why so many people are shocked,” she said. “I mean the beach was packed with people, they were coming down to see what was going on.”

The woman said the emergency services “worked diligently” to deal with an “absolutely tragic” incident.

There have been at least 29 accidental fatalities in open water across the UK since the middle of May, according to the National Water Safety Forum. An East of England ambulance spokesperson said it had dispatched its hazardous area response team, critical care paramedics and two air ambulances.

“Sadly, despite best efforts, two patients could not be resuscitated. One patient was transported by air to hospital, and a further three patients were transported by road to hospital,” they said.

The area is known for its strong currents, though in his response to the incident, the local MP, Bernard Jenkin, told the BBC “we don’t think of West Mersea beach as a dangerous beach”.

Anyone who was in the area at the time and has information or footage that may assist the investigation is asked to contact the police on 101 and quote incident 1090.