Sarah, a competitive swimmer in high school, longed to slip into the cool waters of the bay but didn't relish the idea of such a cold dip. This afternoon, Sarah and Bill were watching the kids build sandcastles, while they idly sipped beers under the shade of a beach umbrella. Sarah followed their adventure with half an eye, finding her summer romance novel more fascinating. Her thighs were getting sticky - the afternoon was warming up - and her little gyrations were making Sarah wish for more privacy. With a wet finger she began gently stroking her clit, wondering if she had enough time to cum before Bill and the kids returned.