Police have named the woman whose body was found in the Waikato River on Wednesday night as Beth Christina Winfield.
The 23-year-old Hamilton woman's body was found in the river near Ann St. Police are treating her death as unexplained.
They're looking for the owners of a black Subaru station wagon which was parked on the banks of the river on Wednesday afternoon.
Ms Winfield was believed to have been throwing a ball and playing with her two dogs on the river bank at the time.
The car was parked in the reserve area throughout the afternoon with loud music playing, police say.
They want to hear from anyone who saw the car.
Ms Winfield's body was later found in the river a short distance from where the vehicle was parked.
Waikato police say their sympathies are with Ms Winfield's family and friends.
Any sightings or information can be passed on to Detective Sergeant Terri Wilson on (07) 858 6200 or anonymously via Crimestoppers on 0800 555 111.