They believe he is a black Belgian shepherd. He had no collar and no microchip.
At first, the Chicago Police Department Marine Unit sent one person onto the lake to attempt a rescue. But the dog ran away.
The dog came close to just walking back on the shore but then darted back out on the lake.
Crews were able to use a tranquilizer to calm the dog down around 10:30 a.m. That allowed rescue crews to get close enough to capture the canine and bring him safely to shore.
Someone on the shore spotted the dog around 7:30 a.m.
It seemed the dog didn't know how to get back on land, or he was in no hurry to leave, dodging rescuers' attempts to corral him on one side of the pier. In the meantime, the police had to make sure they were the only ones working to rescue the dog.
"People wanted to help, but we had to -- as much as they want to help, we have to ensure our safety," one police rescuer said.
After a couple hours chasing the dog and trying to usher him toward the shore, he finally got close enough for animal control officers to shoot a tranquilizer dart at him.
Officers with the marine unit tethered themselves to the shore and carefully went onto the ice, crawling toward the dog.
"The marine diver can fall in at any time, so we want to make sure we know where we are in placement and make sure we get the dog to a safe area to tranquilize the dog," one rescuer said.
The sedated dog was brought back to the shore and carefully placed in the animal control truck. Marine unit officers say they were happy with the turnout.
"We have human beings that fall through the ice and get them out. It's tricky. We did very good. It is similar," said one officer.
Police say the dog appears well taken care of. Animal Care and Control say the dog is a 1-year-old male shepherd mix.
Animal Care and Control says if it is determined the dog is a stray, he will be there for the next several days until they can arrange to transfer him to another shelter.