I don't even know where to move this post. You put it in the Messenger forum. As volker says, the Messenger has no maps. In fact, the Messenger has such a tiny display that maps are impossible on the device.
I believe that inReach devices which do have mapping capability can use Garmin's lake charts. For example, the 67i lists various coastal charts among the available maps. https://www.garmin.com/en-US/p/890109#maps
