Seventy-seven-year-old Joseph Sandle hadn't been seen since early Sunday on the 1400-block of South Indiana.
Early Monday morning, officers patrolling Lake Shore Drive and the Museum Campus found Sandle near the water's edge along the southern end of Grant Park.
"He was moving his body toward the water, so I grabbed his waist and tackled him to avoid him jumping to the water," said Claudio Salgado, Chicago Police Dept.
Officer Salgado says Sandle was transported to Mercy Hospital for observation before being returned to his family.