Mich. Comp. Laws § 324.79301: “Political subdivision” defined.

Sec. 79301.

As used in this part, "political subdivision" means any local unit of government or port district of this state and any other governmental agency or subdivision, public corporation, authority, or district in this state, which is or may be authorized by law to acquire, establish, construct, maintain, improve, and operate harbors, channels, and other navigational facilities. Whenever used in this part, the term political subdivision includes any combination of political subdivisions acting jointly.