Mishnah Berurah — משנה ברורה

From a sitting position - For then he will certainly reveal his body, and a person must conduct himself with modesty and shame before the Holy One Blessed Be He; even when it is nighttime and he is in [the privacy of] his own room, behold, "the entire world is full of His Glory" (Isaiah 6:3), darkness and light are the same before Him. And one must always be careful, for this same reason, unless there is no other way, from revealing one's body, even a little, whatever is normally always covered with clothing; but it is permitted to reveal one's arm, up until his elbow, and one's neck, up until the breastbone; therefore, [regarding] socks, one should put them on and remove them under the sheets so as not to reveal his feet which are normally always covered in these countries, for no one walks barefoot, even in the summer. And so too anything similar, unless there's no other way [to get undressed/dressed without revealing parts of the body that are normally covered]. And so too in a bathhouse where it's normal for people to walk around naked, and there's no other way (ie. you can't wash yourself with your clothes on), there's is no issue of immodesty; and similarly when one is washing in the river, the law is the same (ie. you can't wash yourself with clothes on), except that one should be careful to remove and put on one's clothing as close to the river as possible so as not to walk uncovered unnecessarily, and one does not even need to cover their genitals when descending into the river, and not only that, but one that does cover them up appears as if he is embarrassed about it (ie. about his bris milah) and as if he denies the Covenant of Avraham Avinu; however, when ascending from the river, where one is [potentially] now facing others, he should hunch over or place his hands over his genitals to cover them, as long as he does not [actually] touch them as will be explained at the end of siman 3. It's brought in the Talmud - "The cloak of a Torah Scholar is one where no skin can be seen underneath" (ie. it covers the entire body). But [nowadays] we are not careful with this because everyone goes out with pants [and socks] and the skin is not seen [anyways].