There was absolutely nothing to do in this small town our parents moved to in the middle of nowhere. Even the internet and phone service was unreliable, making sitting around the house so boring. About the only thing there was for my kid sister, who was three years younger, and I to do to entertain ourselves was the beach on the lake on the far side of our parents property. It was close enough to walk to but separated enough from everything by the copse of trees you had to go through that it gave a real sense of privacy.

One day, while I was swimming, enjoying the cool crisp water, and she was sitting on the sand watching me, an idea came to mind. Had she ever seen a boy naked before? I thought that I would play a naughty prank on her. As a horny teenage boy, especially one living here in this town where prospects for girls were very limited, the temptation became irresistible to have a little fun and gauge her reaction.

I reached down and shucked off my swim trunks, freeing my hard-on. As I walked out of the water a smirk spread ear-to-ear on my face. I might not have the the most developed boy, but there was enough to my growing boner that it could swing proudly as I strode naked up the beach with a deliberate waggle of my hips.

If she had looked away or complained, or even got up and ran, that would have been the end of it, but she didn't, just sitting there stunned as I closed the distance. She was just old enough to be getting out of the 'boys are icky' phase. Her eyes were mesmerized, and I could see her nipples begin to harden under her little bikini top.