Police have confirmed a 12 year old girl from Buckinghamshire and a 17 year old boy from Southampton died after yesterday's incident on Bournemouth beach.
Ten people got into difficulty in the water - although it's not clear how.
A man's being questioned on suspicion of manslaughter.
In a statement, Buckinghamshire Councillor Anita Cranmer, Cabinet Member for Education and Children's Services said: "Buckinghamshire Council is saddened to hear the tragic news of the death of a 12 year old girl from High Wycombe yesterday on Bournemouth beach. Our thoughts go out to her family and friends. We will be offering support to them at this very difficult time."
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