Many thanks to fmrcaptevil
for pointing me in the right direction to find my sensor. In case others are having the same problem, on my 2006 Safari SE FB, the fresh water sensor is on the road side under the refrigerator. I measured on the outside to determine where the center of the fresh water tank was and carried the measurements inside. I removed the access panel at the back of the shallow compartment under the refrigerator and could see the sensor through an opening in the flooring and a small maze of wires and plumbing, but couldn't reach it. I extended the access to the tank by cutting out an extension of about 3" X 4" so I could get my forearm in and also a wrench to start loosening the sensor which is screwed into the side of the tank, not the bottom as I had envisioned.
There is a wiring harness for the three tank sensors with the wires labeled and very nicely colored with a black wire going to the black tank, grey for the grey and tan for the fresh. That should be a help if I have to start tracking down the other sensors.
Steve Barth at Catcon was a great help to me when I was talking with him but he advised me that the sensor was accessible from the wheel well and that kept me going in the wrong direction. The sensor is well shielded from road debris so on the 2006, corrosion should not have been an issue in failure. The area was clean and dry.
Now I have to fill the tank and recalibrate the system to determine if it's functional but at least I'm finally making progress. Getting anxious to roll her out of the barn and hit the road!