Want to mail something to a ship sailing the Great Lakes - you can do that. They've even got their own Zip Code and there's a nearly unknown post office in Detroit that handles Great Lakes shipping mail: the Detroit Marine Post Office, Zip Code 48222.

The floating post office is also known as the boat the J.W. Westcott II. The boat makes regular mail deliveries to freighters as they pass beneath the Ambassador Bridge leaving from its dock at 24th Street in Detroit, pictured above.

And the mail gets to these ships via their special post office by using this address:

Vessel Name
Marine Post Office
Detroit, Michigan
48222