Putting Intracostal Waterway into google, even a city like NY (shows system connecting Great lakes), which I did before posting, comes up with masses of information, none of which produced an overview map.
So no details to work from, that's why I needed a map
You're welcome. In the USA charts are considered to be in the public domain and free to the populace, hence a site like that one. When you buy a chart you are paying for the printing and "packaging". Wish they'd take the same view here - fat chance!