A 17-year-old-boy and a girl aged 12 have died, and a man in his 40s has been arrested on suspicion of manslaughter following an incident off Bournemouth beach, Dorset Police said.
The force said it received a report from paramedics at around 4.30pm on Wednesday afternoon of people requiring assistance on the beach off Bournemouth Pier.
Emergency services attended the scene and 10 people were recovered from the water.
The force said that a 17-year-old boy and a 12-year-old girl sustained “critical injuries”, and later died in hospital. While the other eight people were treated for injuries that are not life-threatening.
An investigation has been launched and a man in his 40s, who was on the water at the time, has been arrested on suspicion of manslaughter.
Detective Chief Superintendent Neil Corrigan, of Dorset Police, said: “Our thoughts are with the loved ones of the young people who tragically died and we are doing all we can to support their families.
“I understand the beach was very busy at the time of the incident and I would ask anyone with information that may assist our enquiries to please come forward.
“We are at the early stages of our investigation and would ask people not to speculate about the circumstances surrounding the incident.”