The Chronicle reports the 30-year-old Packwood woman and a man were in a car at a boat launch having sex Wednesday night when the deputy stopped them and asked for identification.
The sheriff's office says the woman had a felony arrest warrant, which apparently prompted her to run into the river. She refused to come out and had to be pulled out about an hour later by rescue firefighters.
She was taken to an Olympia hospital where she died Thursday morning. The Thurston County coroner's office is investigating the death.