Genesis 3:25 says, "And they were both naked, the man and his wife, and were not ashamed." Before the fall, God's creation was without flaw, both in condition and perception. Unfortunately, this situation was shortly to change. In fact, one of the first results of Adam and Eve's sin, was that they hid themselves from God because they realized they were naked, and this made them afraid.
This response of Adam and Eve, is an early indicator, that in our fallen condition, it is no longer comfortable or normal for us to be uncovered. Adam and Eve created clothing immediately (Gen 3:7), and God reinforced this behavior (3:21). They created themselves "aprons" which in the Hebrew is like a belt, hanging from the waist and covering what's below. God make them coats, a more complete covering.
In Genesis 9:18-24, Noah has suffered an awkward moment. Of course, if he hadn't gotten drunk, he could have saved himself the embarrassment and his family the grief of consequence; however, in regards to the topic of modesty, I feel it important to note the different responses of his sons.
Ham discovered his fathers nakedness, and not only did he not turn away his eyes, but he made a joke of the situation. Then he tried to get his brothers to do the same. Shem and Japheth showed much more discernment and respect. They refused to share their brothers impropriety, and even at their father's worst moment, they showed him respect.
In our society, nudity is a big joke. We are used to seeing people run around half dressed. In modern entertainment, nakedness is often made attractive, desirable, or laughable. I know that I have been guilty of laughing, and this passage makes me realize that God's NOT laughing. Lord, forgive me for my insensitivity to what You call pure!