Police said there were five people in the car but three managed to get out of the vehicle before it submerged.
Divers located the victims still in the front of the car several hours later.
The two victims are identified as 20-year-old Marielle Carson and 21-year-old Latisha Ray, both of Chicago.
They were students at Southern Illinois University and John Logan College in nearby Carterville.
The Jackson County coroner listed the cause of death as drowning. Toxicology results are pending.