The victim has been identified by the Missouri Water Patrol as Andrew L. Williams of St. Louis.
The body of the 18-year-old man has been pulled from the Missouri River in south Boone County. The Boone County Fire Protection District said Williams, who could not swim, was fishing with an uncle and cousin when he waded into the water and fell into a deep spot.
The others formed a human chain and tried to pull him to safety but lost their grip on him. The incident happened near Cooper's Landing off a sandbar that sits at the mouth of the Perche Creek.
Williams went under around 2 p.m. and his body was recovered in the same area about three and a half hours later.