Police said the child went tumbling several feet into Lake Michigan, nearly drowning early Monday afternoon near the north end of Navy Pier. He was walking with an adult on the path next to the lake, when somehow, he ended up falling into the water.
Divers with the Chicago Fire Department pulled the child to dry land before rushing him to Lurie Children's Hospital in full cardiac arrest.
Investigators said the boy spent hours undergoing treatment as police remained at Navy Pier, working to determine what exactly how this happened.
"As with incident involving children, these are difficult circumstances, and again, we ask that you keep the family in your thoughts," said CPD Deputy Chief Gabriella Shemash.
The 3-year-old was last listed in "very critical" condition at the hospital.