An 11-year-old girl who went missing at a water park near Windsor on Saturday has died, police say.
The girl's death is being treated as unexplained and an investigation has been launched.
"This has been an extremely traumatic and upsetting incident for all involved," superintendent Michael Greenwood said.
"I am aware that several members of the public entered the lake shortly after the girl got into difficulty, but were unable to locate her.
"I would like to commend them for their courage and bravery."
Police were called at about 4pm to reports of a young girl getting into difficulty at Liquid Leisure. About an hour later, they found her, and she was taken to hospital, but she did not survive.
The girl's family have been informed, although formal identification is still pending.
Girl went underwater 'and didn't come back up'
One witness, who had been at the park with her children, told Sky News the girl was seen going under the water and "didn't come back up".
"At that point, the lifeguards came running," she said.
"She was with a group of friends for a girl's birthday," said the mother, who did not want to be named.
"My daughter spoke to the birthday group."
Members of the public who were at the activity park were asked to call her name on the beach, in case she had got out of the water and was back on land.
"But no one found her," the witness said. "The lifeguards were working incredibly hard.
"After about 30 minutes, we were asked to leave the beach, just as the ambulance and fire crew arrived at the site. There was a police helicopter, air ambulance, and a boat for search and rescue.
"I saw one of the adults from the group which the girl had been with, and I asked if I could do anything to help, and she just asked that I prayed for her."
'No corners were ever cut on safety'
Gavin Springett, who worked at the park last summer putting in all the operation training and safety requirements, told Sky News: "No corners were ever cut on safety".
"I actually couldn't sleep last night thinking about it," the former operations director said.
"Like all lakes, the depth of water can change quite dramatically.
"I can't imagine how the owner and staff are feeling I just hope they are being given the support required."
He said there are extensive safety measures throughout the park including "lifeguards on multiple areas of the park, there will be one or two on the beach, and one on every section of the inflatable courses".
"They are also open water swimming trained, and they do staff training monthly on water rescue."
"Buoyancy vests are compulsory on all inflatables even for adults," he added, and "the whole park is covered with CCTV."
Staff 'asked customers for goggles' to look underwater
A second witness told Sky News: "We were waiting to go on things and lifeguards were running all over the obstacles and looking under them.
"They were dismantling the Ninja Warrior near the beach, looking for her.
"Staff actually started asking customers for goggles, to look for her underwater."
Liquid Leisure said it would be closed on Sunday.
"Our thoughts and prayers are with the family, friends and all those affected by this desperately tragic and upsetting incident," it said.
"As Thames Valley Police are in the early stages of an investigation it would not be right for us to add further comment, but we will continue to fully support and assist them throughout the process."