It would depend on whether you are using a lubricant, shower gel or moisturizing soap. If you are only using water your skin will began to break down. After 4-5 your skin will show dry spots when after off. A few more and you will note your skin will began to dry "prunish."
After the 20-you will look like you have dry spots that can break your skin down to began molding in spots! So save the water and just day dream!
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