A 17-year-old-boy and a 12-year-old girl have died following an incident off Bournemouth beach.
Dorset Police said a man in his 40s has been arrested on suspicion of manslaughter.
Emergency services attended the ‘multi-agency’ incident earlier today and 10 people were recovered from the water.
Dorset said they received a report from paramedics at around 4.30pm on Wednesday afternoon of people requiring assistance on the beach off Bournemouth Pier.
Ten people were recovered from the water but the 17-year-old boy and 12-year-old girl had suffered critical injuries. Police said they were taken to hospital but died later and their families have been informed.
The force added that eight other people were treated at the scene for non-life threatening injuries.
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.”
South Western Ambulance NHS Foundation Trust (SWASFT) said it sent multiple teams to the scene including two air ambulances, six land ambulances and a critical care car.
The coastguard said it searched to “make sure there were no other people missing” and was “satisfied there are not”.