I didn't fish shallow to find out the one day I was out there. We fished mostly new spots looking for something different. Only caught a few bass and a sheepshead in water mostly deeper than 15 feet.
Lots of people are saying the Michigan waters are slow and tough since spring. Most of the better catches seem to be coming from Ontario waters and still mostly deep though current can pull some bass shallow anytime in key spots.
I imagine this hot summer drove lots of bait into deeper water and the bass go where the bait is. I was out a few weeks ago and we found lots of bass way out in the lake around schools of minnows that they sometimes busted on the surface even though that was infrequent. We could see more bass than we were actually catching so the bass were there even if we weren't always catching them. They probably got a good education on lures this year so sometimes the bite is more particular than it has been. We found a few spots that the bass were biting really good in but you could tell they were actively chasing and chasing bass, especially in groups, usually aren't as hard to catch.