A teenage girl and a woman in her 40s have died after getting into difficulty in the water off the Essex coast, police said.
Emergency services were called to the scene in West Mersea, near Colchester, at 5.35pm on Wednesday following reports of several people in difficulty in the water.
Essex Police confirmed that, despite the best efforts of paramedics, a teenage girl and a woman in her 40s died.
A third person remains in hospital in a serious condition, and two other people are in hospital with non-life threatening injuries.
The East of England Ambulance Service said one patient was transported by air and three patients by road to hospital after the incident near the Sea View Holiday Park.
"Following reports of multiple people in distress in the water at Sea View Holiday Park, West Mersea yesterday evening, we dispatched multiple resources including our Hazardous Area Response Team, critical care paramedics and two air ambulances to the scene," a spokesperson said.
"Sadly, despite best efforts, two patients could not be resuscitated."
On Thursday morning, Detective Chief Inspector Al Pitcher said: "Today, 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 enquiries.
"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."
Police believe the people involved in the incident knew each other.
Images from the scene show police officers on the beach and ambulances parked nearby.
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In a statement on Wednesday, the force asked people to avoid the area.
"While we remain on scene, we would ask the public to avoid the Seaview Avenue and beach area," their statement said.
"We appreciate that this will cause some local issues, but would ask for your patience and understanding as we may be there for some time yet."
The coastguard rescue team described Wednesday's events as a "tragic incident".
Police have asked for anyone in the area at the time or who may have footage of the incident to contact them.
There have been numerous drownings in the UK over the summer, including during the May heatwave when at least 15 people, mostly children, drowned while swimming in open water.
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