Shelf ice or sand? Group urges caution after man plunges into Lake Michigan Updated Jan 28, 2021; A man plunged into Lake Michigan this week when he thought he was walking on sand; it was shelf ice covering the lake’s surface along the shoreline. Walking on shelf ice is extremely dangerous, Dave Benjamin, executive director of the Great Lakes Surf Rescue Project, told The Times. At the same time, it’s difficult to know where the sand ends and the shelf ice begins. Johnny Jacobsen, of Chicago, learned that the hard way on Tuesday, Jan. 26, when he and his wife were walking along Loyola Be...