Indiana Dunes
I don't have too much to say about Indiana Dunes. It's a fresh water beach in the mid west.
The dunes are impressive getting up to a little over a hundred feet in height which is exhausting to climb. The only place I have run into thicker mosquitos than was up in the woods of Maine so don't forget your bug spray if you do visit.
There's an Indiana Dunes State park adjacent to the National Park, and honestly it was a lot cooler than the National Park, although the 2 mile hike to the beach in the National Park may get you a slightly more private experience than the parking lot adjacent state park beach so pick your poison.
It's a neat place if you aren't too far away, but I saw plenty of similar places along the Michigan coast while I was there so I wouldn't say there's anything particularly unique or attractive about Indiana Dunes. I'm still glad I checked it out though, and it's certainly worth visiting if you're in the area.