The child was pulled from the water at Waveney River Centre, at Burgh St Peter, near Beccles, just after midday.
She was taken to James Paget Hospital in Gorleston where she died four hours later.
Police said her death is being treated as unexplained but it is not believed to be suspicious and they are continuing to investigate.
Forensic officers were at the site earlier carrying out inquiries.
A seven-year-old girl has died after being found unconscious in a swimming pool at a holiday resort in Norfolk.