After doing a number of measurements under the house and in the bathroom, Lisa first drilled a pilot hole in the floor of the bathroom, then drilled a larger hole through which conduit will run to carry the new 30A circuit for the electric water heater. She also tried running the wire through the conduit, but that didn't work out that well and we'll have to try again later; it's just too much wire to push at once without a pilot string, it appears.
This sounds simple, but it was not. Lisa was back and forth under the house about a dozen times today. This is dirty, messy work, and she was pretty worn out when she was finished. Thank goodness she's wearing coveralls, a dust mask, goggles, and heavy leather gloves.
My contribution was to pull on stuff passed through the hole and to fetch and carry things upon demand, but Lisa did most of the work. She says that once that conduit (and the wire) is up through the floor, we're about 97% done with the stuff she has to do. At that point, we call our plumber and say, "We're ready; bring on the water heater."