An autistic teenager who was a "brilliant swimmer" drowned after having an epileptic seizure in a swimming pool, an inquest has heard.
Hayley was a member of swimming club the Newport Seals
Hayley Williams, 13, from Newport, a Britain's paralympic team hopeful, died during a lesson at Ashgrove Special School in Penarth, last December.
She failed to resurface during a dive into the hydrotherapy pool.
A verdict of accidental death was recorded by Cardiff and Vale Coroner Mary Hassell.
Hayley was diagnosed as autistic and epileptic at a young age and attended the Vale of Glamorgan school which encourages its pupils to participate in sport.
The inquest heard that the teenager was so prone to seizures that she had to wear a helmet in case she fell over and hit her head.
Head teacher Brian Bayford told the court: "Hayley was fiercely independent and swimming was the only thing that she was truly brilliant at.
"The fact that she was epileptic would not have affected my decision to let her swim. If there was ever an acceptable risk - this was it."
Her teacher Charlene Lyle said Hayley was by far the best swimmer at the school.
"She swam, like a dolphin - she was such a beautiful swimmer. It would have been like caging an animal to stop her doing it.. She loved it.
Hayley was given first aid at Ashgrove Special School
The inquest heard there were six adults in the school hydrotherapy pool along supervising six children on the day Hayley died.
Her personal supervisor was afraid of water and was watching from the poolside but another member of staff was "within arms reach" when she suffered the fatal seizure.
The hearing was told that Hayley began diving in and out of the pool and just moments later she disappeared underneath the water.
A learning support assistant in the pool noticed she had not come back up and went to her rescue.
Hayley was treated by first aiders at the school and was taken to hospital where she later died.
Her mother Gaynor Williams told the hearing: "I don't want to blame anyone but I think the person who was meant to be on a one-to-one with her should have been at her side at all times.
But she said the "great joy" of her daughter's life was swimming.
"There is no way we would have allowed her to stop just because she was epileptic."
Coroner Mary Hassell said: "It was clearly a risk letting her swim but it was balanced against the great joy she got from swimming."