CHICAGO (CBS)–A boating accident Sunday on the Fox River Sunday severely injured a 6-year-old boy from northwest suburban Cary.

The boy was swimming in the river in the small community of Fox River Grove, near Picnic Grove Park, when he was struck by an 18-foot Bayliner motorboat as it approached the shore to dock, police said.

Police said the boy dove under the surface of the murky water, and the boat’s 19-year-old driver did not see him as he approached.

Bystanders spotted the boy floating on the surface of the water, and began performing CPR before paramedics arrived, according to police.

He was airlifted to Advocate Lutheran General Hospital in Park Ridge with life-threatening injuries.

Police said alcohol is not considered to be a factor in the accident, but the McHenry County Sheriff’s office is still investigating.