Agree with most comments. In more than 40 years of RV Camping, including dry sites, we have always taken "Navy" showers. Adjust the water temp, wet your body, turn off water at shower head, soap up in all the right places, turn the shower head toward the wall, turn it on, rinse, repeat as needed. All of our rigs the shower water came back on cold for a second or two, then OK.
Best shower I ever had was at Red's Meadow behind Mammoth Mountain, CA. Geothermal water heated to perfection!! However, "Goldie" the campground host bear was always waiting outside the shower door when I finished. I learned to bring along a large dog bone everytime I showered there.