Emergency services were called to the river near Cheapside, Stourport-on-Severn, shortly before 6.40am on Tuesday.
North Worcestershire Police said they found a woman in the water behind the old vinegar works, "clinging to the ledge of an old boarding pontoon 10 meters from the river bank".
"The lady was assessed and had serious injuries," the force added. "She received treatment at the scene & was transported to hospital."
West Midlands Ambulance Service and Hereford & Worcester Fire and Rescue Service also attended the scene.
The fire service said the woman was helped from the water using a rescue sled.
A spokesperson for West Midlands Ambulance Service said: "We were called at 6.36am to an incident in the water nearby to Cheapside, Stourport on Severn. One ambulance, two paramedic officers and Hazardous Area Response Team (HART) paramedics attended the scene.
"Upon arrival we found a woman. She was assessed and had serious injuries. She received treatment at the scene and was conveyed to Worcester Royal Hospital for further assessment."