What are Federal Waters?
The Federal Code of Regulations (46 cfr 10) requires anyone taking consideration (money) from a passenger to be on a vessel on federal waters, to have a merchant mariner credentials (Captains License). So what are federal waters? Normally if it is connected so as the water flows to the ocean, it is federal waters.
However, nothing is that clear cut. US Army Corp of Engineers, US EPA, and USCG are involved in designating federal waters.
listed below are links to PDF file which indicate what waters are federal waters. This is not an inclusive list. If in doubt call the headquarters office for that area.
Illinois, Indiana, Michigan, Minnesota, Minnesota upplement*, New York, Ohio, Pennsylvania and Wisconsin