Keep away from those DC boaters they are a strange bunch.
The lower yough is pretty low right now, so the falls are legal. Drive up to Ohiopyle and huck your balls off, then go for a loop lap (a large horseshoe bend in the river allows you a short hike back to the put-in).
Great falls is quite dangerous, if your competent then great, if not stay away. More times then not, a swim prompts the public spectators to call 911 for a rescue. Its in a national park so boating is tenable at best.