What type of graph would you recommend for Lake St. Clair in order to find scattered rock beds where smallies hang out?

I typically fish 4-16' deep on expansive flats.  Looking to pinpoint some piles.

A unit with GPS mapping and high def maps is the kind of unit you want. The cheapest depth finders will easily show you the rock piles. Good GPS maps will let you drive right to them without having to spend hours driving around looking for them. Just pick the unit with either built in maps or buy map chips. Get the biggest screen your budget can afford.

You just got good adviice there.  Go some place where they sell them and get some hands on time with different brands.

You're looking so shallow your cone is very small and you'd have to run right over the rock pile to see it.  Side finder will help along with the maps.