I went off on a rabbit hunt looking for a path through the floor for an extension cord for an extra space heater last week, before our T-day trip.
I started with the access panel under the bathroom sink. The plumbing and wiring head aft from there. Aft is under the closet with a drawer under it. I pulled the drawer out and, bingo...
The hole looks down on both sides of the metal panel with the City water connection on it, right into the utility bay.
And, this hole is another potential source of certain aromas that might be entering the coach.