One of my favorite rules of childhood: it does not matter how long you have actually worn a garment, nor what kind of activity you have engaged in while wearing said garment; once the article of clothing has touched your skin and been removed, it is automatically dirty and should be discarded into the laundry hamper. Note: all horizontal surfaces in bedrooms and bathrooms can be used for a hamper at any time. Exception: if you have an "accident," it is perfectly acceptable (indeed, preferable) to hide the offensively odorous garment in a tight corner of your closet or drawer. Moms like finding those presents.
This afternoon, when Dad the permissive returned from work, the kids went swimming.
It was not warm enough, but it satisfied some need buried within them. Plus now they know where their swimsuits are when the temperatures hit the 80's... tomorrow.