A 38-year-old woman from Red Earth First Nation died when the vehicle she was in went into water.
The crash on the reserve happened around 6:30 Saturday morning.
Investigators say the car remained upright, but was partially submerged.
The woman was pronounced dead at the hospital in Nipawin, while the driver of the car was transported to hospital in Saskatoon with serious injuries.
Police say they are still investigating, but they believe alcohol was involved.