At 10:54 p.m. a call came in from a passerby that a car had driven into the river from Kelly Drive near Boathouse Row.
Investigators believe the driver swerved to avoid a car that crossed over from the northbound lanes of traffic.
Police say a male passenger was able to swim to safety but the search was on for the female driver.
Marine units were called out to the scene, and police, the fire department, and medics helped in the search for the driver in the water, which was rougher that usual due to the rainfall.
Philadelphia Police Lieutenant Scott Drissel explained, "It's obviously a dangerous situation for the divers, but they did an admirable job getting in there and putting their life on the line. And, unfortunately, we weren't able to get there in time."
It was around 12:45 a.m. Monday when, with the tow hooked up, crews hauled the car out of the river.
"When we got the vehicle out of the river we recovered another occupant out of the vehicle, who was unfortunately deceased," said Lieutenant Drissel.
Police have not yet released the driver's identity, but they say she was a 21-year-old woman from Darby, Delaware County.