Individual maps are included for the following (scroll down page): Lake Huron and Erie, Lake Ontario, Lake Michigan and Lake Superior.
From the creators: "This series of river maps is done up in a style inspired by urban transit maps such as those pioneered by Harry Beck in the 1930s for the London Underground. Straight lines, 45-degree angles, simple geometry. The result is more of an abstract network representation than you would find on most maps, and it’s not meant to be taken too seriously — I would not recommend actually transiting through these rivers, as many portions of them are not navigable. But they do, nonetheless, connect us."