Crews could be seen searching the waters near the enclosed boating area, also known as the "Playpen," close to downtown.
After about an hour of searching for the 58-year-old man on Saturday, crews called off the search for the night.
Divers were back on Sunday, but there was no word yet if anyone was found. The search was suspended once again.
A witness who was out on the water says the Playpen was very busy when first responders arrived on scene. He recounted what he saw.
"All of a sudden, we started seeing helicopters flying around and a lot of ambulances and fire department and the dive squad and all that stuff so we knew something was up," Ted Widen said.
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Dave Benjamin, the executive director of the Great Lakes Surf Rescue Project, says with Sunday's forecast calling for windy conditions, people need to be especially careful out on the water.
"Unfortunately, we see this every year because there's a lot of people that go to the playpen," Benjamin said. "Alcohol may be involved. It's very crowded. And a small incident of falling off a boat could have a fatal consequence."
Benjamin said choppy waves could pose very dangerous conditions for those out on the water.
"We just don't want somebody's family fun day at the beach to turn into tragedy that they then have to live with, and compounding it on Father's Day tomorrow," Benjamin said. "We know that there's going to be a lot of people the beach. It's going to be hot. People want to get out there and have some fun, but keep the inflatables at home from the south end of Lake Michigan and going north, understand the water will get more turbulent and several types of dangerous currents."