An 18-year-old man who got into difficulty in the sea in Clacton has died two days after his sister.
Essex Police said Haider Shamas died on Saturday, two days after he and his sister Malika, and a third relative, were rescued from the sea near Clacton Pier.
Floral tributes have been attached to railings by the beach in memory of the siblings from Luton.
A 15-year-old relative of the pair who was also rescued from the sea and is expected to make a full recovery.
Becky Bryant, a carer from Wivenhoe, said the three teenagers were with a group of up to 30 people at the beach.
The incident happened little more than a year after 15-year-old Ben Quartermaine drowned near the pier.
Acting Detective Superintendent Paul Wells said on Thursday that several members of the public aided the rescue effort and two other people were also treated at the beach, but did not need to be taken to hospital.
Witnesses described “distressing” scenes as lifeguards and paramedics scrambled to help the three teenagers after they were spotted struggling near Marine Parade at about 1.40pm on Thursday.
Witness Becky Bryant, 40, said she saw "two people being pulled from the sea and lifeguards trying to do CPR until the paramedics turned up.
“Everyone tried to take turns doing the CPR while the lifeboat went out again and retrieved the third person, who seemed not to be in such a bad way.
“It was so distressing, everyone was trying to do what they could – lifeguards, air ambulance, they truly worked as a team.”
All three teenagers were taken to Colchester General Hospital.
The East of England Ambulance Service said its first responder arrived at the beach less than seven minutes after the call was made.