Police were last night investigating how the girl suffered what was described as “life threatening injuries” as a result of being underwater.
The girl was hauled out of the water at around noon at the Waveney River Centre in Burgh St Peter near Great Yarmouth, Norfolk.
She was taken by ambulance to the James Paget Hospital in Gorleston, Norfolk, and was pronounced dead at around 4pm.
Norfolk Police confirmed tonight her death was being treated as unexplained, but was not suspicious.
Attempts were made to resuscitate the girl at the scene before she was taken to hospital.