Maybe I missed it, but what is the point of the query? Do you wish access somewhere or wish to restrict access?
What is a navigable waterway? This should blow your mind...
http://www.wetlands.com/coe/coe329p0.htm#329.5
Maybe you can read and comprehend it better than me, but it seemed like a muddy issue.
Here is insight from Oregon...
https://egov.oregon.gov/DSL/NAV/sandy_faqs.shtml
Pennsylvania insights...
http://www.fish.state.pa.us/water/pu...lic_waters.htm