Key word is 'navigable waters', on inland lakes and rivers no coast guard licensing is required.
The Kenai River guides still need a CG license to take people fishing on the river. There is a Western Rivers endorsement for this. I'm not sure if a CG license is required for non-power vessels (drift boats), but it's definitely required for power boats.
The Coast Guard requires a special endorsement for the Great Lakes, as well. My Near Coastal license is no good for the Great Lakes. I would need a certain number of documented days (and maybe another exam?) on the Great Lakes to earn the endorsement.
