From the Chicago Trib (via PhysOrg.com):
Forty feet below the surface of Lake Michigan in Grand Traverse Bay, a mysterious pattern of stones can be seen rising from an otherwise sandy half-mile of lake floor.
Likely the stones are a natural feature. But the possibility they are not has piqued the interest of archeologists, native tribes and state officials since underwater archeologist Mark Holley found the site in 2007 during a survey of the lake bottom.
The site recently has become something of an Internet sensation, thanks to a blogger who noticed an archeological paper on the topic and described the stones as “underwater Stonehenge.”
Turtle Talk 