When you are in the Navy, you get used to communal showers and heads. By the time you leave Boot Camp, you have very little sense modesty. If you get stationed shipboard or with the Marines, whatever feelings of shyness about your body you have left is totally torn asunder.
Me, personally, have no problem with nudity. (If my sister-in-law wasn't staying with us, i'd be nude more often. It is to respect HER modesty, not my own.)
Also, I was in the Navy when they started doing random drug screening, and a Master-At-Arms would have to watch you give a urine sample to make sure it wasn't contaminated, that it was your own urine, (Yes, people have been known to, or at least attempt to, substitute someone else's urine sample) and to maintain a legal chain of custody. After all that, you can pretty much go on command, and you don't care who is watching.