A diesel submarine uses a lot of freshwater. It refills the main batteries, cools the main engines, cooks food and washes dishes, and, if there is any left, cleans the crew. We carried some from port, but then had to make it from seawater. Since we did not have steam boilers like a surface ship, we made it using compressor distillers. Our compressors were extremely noisy. Submarines are supposed to be very quiet, especially when there are a lot of bad guys around. So we ran the compressors as little as possible and only when we were snorkeling. To conserve water, each man was allowed one cup a day for hygienic purposes. Most of us used it in the morning to brush our teeth.
Obviously, there were no showers. Nor sponge baths. Body odor was no problem, as our sense of smell went dead after a week or so. But then the green grungies started. Mold. Under our aims and in our crotches. Itchy. Luckily, our corpsman had anticipated this problem and purchased cases of those little bottles of Absorbine Jr. before we sailed. The ones with the sponge over the opening. Worked like a champ, but stung like hell. Armpits were a breeze, but we had to be awfully careful in the nether area.
We went fifty-three days without showers. And the president stared the Soviets down and averted WWIII. I'm still proud of my small part.