Authorities say a man has drowned in northwest Missouri while attempting to retrieve a boat that was adrift on the Missouri River. The Missouri State Highway Patrol identified the victim as 30-year-old Benjamin Hirner, of Mokane, MO. The patrol says he went into the water Friday just north of where the Nishnabotna River flows into the Missouri River in Atchison County. A Nebraska Air National Guard helicopter flew him to a hospital in Omaha, Nebraska, where he was pronounced dead. The Iowa Department of Natural Resources also assisted at the scene.