The Michigan Department of Natural Resources page on the Northern Water Snake says:
Description: A water snake with dark bands or blotches on a light brown or gray background color. Some old adults may appear solid black or brown. The belly is white with reddish half moon shaped markings; some specimens have an orange belly speckled with brown or black. (The endangered Copper Bellied Water Snake has an unmarked reddish or orange belly.) Adult length: 2 to 4 feet.
Habitat and Habits: These snakes inhabit the shorelines of lakes, ponds, or streams. They swim well, seeking food (frogs and fish) and safety in the water, and often bask on objects hanging over the water. Water snakes are not venomous, but will bite if cornered or handled. They are sometimes mistakenly called “water moccasins” (which are not native to Michigan).
Reproduction: Females give birth to their 7 to 9 inch young in late summer. There are 8 to 48 babies in a litter. The young are gray or brown with bold black bands.
Range and Status: Northern water snakes are found throughout the Lower Peninsula and the eastern Upper Peninsula. Needless persecution by humans has eliminated water snakes from many places where they were once common.
The DNR’s Michigan Snake Page adds that there are just 17 species of snake in Michigan, so do what you can to protect this snake and its kin.
More Michigan snakes on Michigan in Pictures.