The whole family went to the beach this summer and it was very nice.  We visited a secluded area of the beach, which meant that the car and beach pavilion were a long walk away. The inlaws were there with me and my wife. Before long, everyone either had to get something in the car or had to use the restroom, so they all decided to go for a hike back to the car and the pavilion area. Only me and my wife's little sister stayed behind. She was sunbathing on a blanket and I was sitting against a post.

She asked me to put some additional sunscreen on her, I agreed so she got up and came over to me. I rubbed the lotion all over her body and all around her swimsuit. I mentioned that she was going to get bad tan lines like this, so she should take her suit off for a little bit. We would be alone for about an hour. "are you sure you wont tell anybody if I do?" she asked. I laughed and said "oh sure, like I am going to tell your sister that I saw you naked!" this would have to be out secret. She took her suit off and moved back to me so that I could rub the rest of the lotion on her.

My hands rubbed all over her body, her tits and ass too. I rubbed her ass and slide my hand down to her pussy and gently slid a finger into it. She looked down at me and said "our secret right?".I took my shorts off and said "Your secrets are safe with me". With that, she allowed me to pull her down on top of me. I slide myself into her all in one motion. She began to ride me and started to purr like a kitten. Before long, she started to cum while she was grinding on me. When she started to cum, it set me off too. I released my load deep inside of her as her pussy spasmed all over my cock. She squirmed all over my dick while she came, it felt amazing. I stayed inside of her for a while as we were both so sensitive. We came well together that day at the beach.

The family came back a while later and had no idea of the erotic scene that took place right there a half hour before.