Beachgoers filmed paramedics delivering CPR to people involved in an incident off Bournemouth Pier that killed two youngsters, witnesses have said.
The deceased - a 17-year-old boy and a 12-year-old girl - sustained "critical injuries" and died after being pulled from the sea.
Eight other people were treated for injuries described as non-threatening. A 40-year-old man has been arrested on suspicion of manslaughter.
People at the scene have hit out at those who filmed emergency services.
Nicola Holton, who was at the beach with her husband, said she witnessed lifeguards entering the sea trying to help "multiple people" who were struggling in the water.
She said she would never forget the image of one person being pulled out of the sea and onto the beach to be given medical treatment.
"[There were] loads of idiots ignoring lifeguard requests to get out of the water and clear the beach," she said.
"People were running towards those having CPR filming on their phones."
A doctor who said he was involved in the resuscitation attempt on the young girl praised the work of the beach lifeguards and also hit out at those filming the incident.
"Those videoing the desperate CPR attempts should think long and hard at their actions, the tragic death of a child is not something anyone should voyeuristically observe", he told MailOnline.
An investigation into the circumstances surrounding the incident has been launched by Dorset Police, the Marine Accident Investigation Branch and the Maritime and Coastguard Agency.
On Thursday morning police said that the two deceased had not been hit by a vessel following reports they had been injured by a jet ski.
Unconfirmed reports say those involved in the incident had been jumping off the pier, which is around 300m long, and were pulled further out by a riptide.
Rips, as they are commonly known, occur when water that has been pushed towards land by the sea, is tracking back out, creating a channel of water which pulls back out to sea.
Rips are often harmless, and swimmers will barely notice them, but typically around large headlands or piers, they can be powerful and drag unwitting swimmers and surfers out to sea, particularly if there is a large swell running.
Tobias Ellwood, the MP for East Bournemouth and chair of the Commons defence committee, told Sky News that the pier was "involved" in the tragedy.
The local council will review its protocols in relation to what can be conducted on the pier, he added.
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