It’s South Milwaukee’s version of the Polar Plunge.
From the Polar Bear Dash 5K website …
START YOUR NEW YEAR OFF ON THE RIGHT FOOT. And then the left! The Polar Bear Dash is a 5k race on New Year’s Day at beautiful Grant Park in South Milwaukee. What sets this race apart from any other 5k race you have done: an optional polar dip into Lake Michigan at the end of the race. There will be a special award to the first few runners who take the dare into the lake immediately after the race.
Of course, the South Milwaukee Fire Department will be on hand to make sure all goes well with the lake plunge. Here is video from their work last year. It looks like it will be another cold one on Friday — high of 22 degrees.