Detectives are investigating the death of a 46-year-old woman in Lake Alexander yesterday afternoon.

Territory Duty Superintendent James O’Brien said the woman had been swimming with friends and relatives prior to her being located motionless in the water around 4:30pm.

“Witnesses provided first aid before police and St John Ambulance arrived and took over administering CPR.

“She was rushed to Royal Darwin Hospital but has tragically passed away overnight.

“Police will prepare a report for the coroner.”