I have a unique issue. I have an older pier and beam home on level, so the crawl space is below ground level. When rains saturate the ground causing flooding, it gets wet under the house (I do have a sump pump). The problem is, especially in cold weather, I have extreme heat loss in the hot side copper line. The gas hot water heater is at the opposite end of the house from the shower and the lines are buried only 6" in the cold, wet ground. Some thoughts I had were replacing supply lines and free hanging from floor joists to get out of the cold wet dirt and or an on demand heater, but The house is old and not much room to add an on demand water heater in the bathroom. Just looking for ideas of things I may not have thought of, especially saving time and money.

I'd get the piping out of the ground, insulate it and strap it to the beams.

Is it a one story house?

Yes, raising the lines is my first thought....when it dries out under there. It is expensive and time consuming, even doing it myself. Yes it is a single story home. I've worked more on drainage around the house, but it seems there is no taming the ground water table in heavy rains.

Run PEX in the attic.