I asked a group of parents and youth (back in the 70's) if they would mind undressing to their underwear.
The point being that most "bathing suits" are worn with the same exposure of skin that underwear covers.
So my question became, "why did they spend so much on outer coverings?"
After the initial shock, the group really got into what was modest and why modesty is important. They began to construct a program of principles that generally came to the following conclusions:
Modesty in men was just as important as modesty in women.
Apparel was not to be worn to embellish some physical attribute(s).
Apparel that would be used in a private setting is not always as private as expected.
What is worn is also a form of worship on display.
Men are not as attractive as they might think if they have too much or too little body hair.
Women's desire to appeal to others is a human appetite that needs moderation just as in any other human appetite.
There are two places in which being immodest is appropriate.
I don't remember off hand the other ones.