A teenage girl has died after three people were rescued from water near Clacton Pier in Essex, with one remaining in a critical condition.
Emergency services, including police and the Coastguard, were called to the scene at 1.40pm on Thursday afternoon.
After being recovered, the casualties received treatment on the beach.
An 18-year-old man and a 15-year-old girl were also rescued.
The 18-year-old remains critical in hospital, while the girl is expected to make a full recovery.
Two other people were assessed at the scene but did not require hospital treatment.
Their injuries are not known at this time.
Speaking to the East Anglian Daily Times, one witness said: "Three of them were pulled out of the water and two of them looked really bad.
"There was members of the public out there giving them mouth to mouth before the beach patrol got to them."
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An ice cream vendor on the seafront added: "It's another tragedy on our beach. It happens every year, there's swimming spots at each end of the beach but these kids were swimming in the middle.
"People come from all over and hey don't know what the waters are like."
A spokesperson for Essex and Herts Air Ambulance service said: "At this time three critical care teams are in attendance: two from Essex and Herts Air Ambulance and one from the East Anglian Air Ambulance.
"They are helping to provide critical care along with our partners from the East of England Ambulance Service Trust and other emergency services."
Local traffic and public transport around the pier is currently being diverted.
Hedingham Buses, who operate routes in the area, tweeted: "Due to a serious accident on Marine Parade West in Clacton, all services are diverting via Wash Lane in both directions.
Emergency services were at called 1.40pm today to reports that three people were recovered from the water near to #Clacton Pier and were being treated on the beach.— Essex Police (@EssexPoliceUK) August 8, 2019
We are all in attendance and the three casualties are still being treated.
Two remain in a critical condition. pic.twitter.com/2YV5vgAho1
"We are also expecting severe delays for the foreseeable future. Our sincerest apologies."
Clacton Pier, which stretches 160 yards (360 metres) into the North Sea, opened in 1870.
It is a popular destination during the summer months.