Both Blue Marsh + Beltsville have large "No Wake" areas. Both lakes have launches in the "No Wake" areas at Blue Marsh the PFBC ramp is up near Bernville on 183. Beltsville it is called Preacher's I believe it is off 209(not sure). I can also tell you they are both patrolled but that still doesn't stop idiots flying around in the "No Wake" zones.(at least at BM). Weekends do get nuts - you are better off fishing the night shift,,,,,, BUT learn the area first........ Fog can be a real issue.
I would think you would be OK on the river as long as you stayed in the lower "dam" areas. I would proceed with caution maybe with a set of eyes up front to watch for rocks till you learn the water. I would also pay attention to water levels + flow - low clear flows in late August/September it will be a lot easier to see hazards.
“Would it save you a lot of time if I just gave up and went mad now?” Douglas Adams