The body or a woman has been found in a car which has crashed into a Fenland drain at some point over the weekend.
Police are appealing for witnesses following the incident near Christchurch.
At 5.35am yesterday officers discovered a black Honda Civic that had left the road at Sixteen Foot Drain near Christchurch and entered the river.
The body of a woman in her 40s was discovered in the vehicle. It is believed the vehicle entered the river between 11.45pm on Saturday (June 4) and 5am yesterday (June 5).
Anyone who saw the vehicle in the area is asked to contact police on 101.