The Columbian reports the woman, who was in her 50s, was wearing outdoor clothing and a flotation device. Search crews also found an empty kayak on the eastern tip of Government Island. Authorities say it appeared the kayak possibly had two passengers.
But a second person was not found Friday after a search of the area.
Fire Department Capt. Scott Willis says the body was spotted by a state Fish and Wildlife crew on a river patrol.
The woman had been dead for about 48 hours and had no identification.