A 14-year-old girl has died and an 18-year-old man is in a critical condition after three people were rescued from the sea off the Essex coast.
The three, who are related, were pulled from the water near Clacton Pier at about 13:40 BST, police said.
All three were treated on the beach by paramedics before being taken to hospital.
A 15-year-old girl is expected to make a full recovery, police said.
Acting Det Supt Paul Wells said: "At this early stage, we believe that three teenagers got into difficulty at sea and were recovered from the water, close to Clacton Pier.
"A teenage boy and a girl were taken to hospital in a critical condition. Of these, a 14-year-old girl has died in hospital, an 18-year old man is stable but remains in a critical condition.
"The three casualties are related. Immediate family members have been informed and are at hospital. We are continuing to support the family at this unimaginably difficult time."
Anu Cooray, 37, from Watford, told the BBC: "We saw the lifeguards running and ambulance paramedics.
"They were doing chest compressions. Three helicopters came. One of them was really bad. We were so sad to see it."
Ambulance crews, coastguard and police were called to the scene and Clacton RNLI said they were also called out.
An East of England Ambulance Service spokesman said it was called to the incident at Marine Parade, Clacton-on-Sea at 13:34 BST.