Emergency services were called to Liquid Leisure, near Datchet, at 3.55pm on Saturday after the youngster was reported missing.
She was found just after 5.10pm and rushed to Wexham Park Hospital, where she died.
Liquid Leisure said the aqua assault course will remain closed for the rest of the week “out of respect” for her family.
In an update on Tuesday, Thames Valley Police said the incident is not being treated as suspicious and a file is being prepared for the coroner.
The victim’s next of kin continue to be offered support by officers.
Meanwhile, a public inquiry into the matter is to begin on November 8.
Flowers and messages were seen outside Liquid Leisure’s closed gates on Tuesday as tributes poured in following the girl’s death.
One read: “To a beautiful little girl.
“I hope you know how hard everyone tried to save you.
“You were just too beautiful for this world. You will always be the brightest star in the night sky forever 11″.
Another said: “RIP little angel, lots of love the Morgans xx.”
Detective Inspector Stuart May, based at Windsor police station, said: “The thoughts of everyone at Thames Valley Police continue to be with the victim’s loved ones after such a tragic incident.
“We have conducted a thorough investigation and have not identified any suspicious circumstances so a file will be prepared for the coroner.
“We have been liaising with the council’s officers who will now take over responsibility for the investigation to determine any potential breaches under relevant health and safety legislation.
“Once again, I would ask that the victim’s family and friends’ privacy is respected at this extremely difficult time.”
A spokesperson for the Royal Borough of Windsor & Maidenhead said: “This is a tragic incident and our thoughts and deepest condolences go to the family and friends of the girl during this most difficult time.
“We have been liaising with the police during their stage of the investigation.
“We are now taking over responsibility and conducting a health and safety investigation to determine any potential breaches under relevant health and safety legislation.”
A Liquid Leisure statement said: “Our thoughts and prayers are with the family, friends and all those effected by this desperately tragic and upsetting incident.
“As Thames Valley Police are in the early stages of 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.”
The attraction’s website says: “Liquid Leisure is home to Europe’s largest aqua park and the first official Ninja Warrior UK aqua park, set on one of the most beautiful private freshwater lakes amongst stunning parkland in the heart of Berkshire.”
Emergency services, including Royal Berkshire Fire and Rescue Service, Buckinghamshire Fire and Rescue Service, Surrey Fire and Rescue Service and South Central Ambulance Service, were at the scene on Saturday afternoon.