Green orb in Michigan

I am pretty sure we were camping up near Petosky, Michigan.  My dad’s cousin and his wife and kids were camping with us, as was our yearly tradition.  
Our tents were on flat ground between the main dirt road and a hill.  On the other side of the road was the beach and then Lake Michigan.  I don't recall what was on the other side of the hill.  It was night, perhaps 8pm, and I was in the tent.  I think everyone else was out around the campfire.  
I heard a commotion and came out.  Many people from other campsites, and my family, saw this 4-5 foot diameter green ball coming across the surface of the lake.  Its origin unknown and it appeared to be mere feet above the water the whole time, which was 10-15 seconds. 
It then floated across the beach, bounced off the road, and went over the hill.
There were no reports of any incident in the papers the next day, despite the 20-30 witnesses.