Her suggestion was music to my ears. An outdoor threesome sounded like one hell of a lot of fun and the idea of watching her fucking another guy again aroused me intensely. We walked hand in hand again down the beach, both of us stark naked. Andrea's nipples were fully erect, pointing upwards toward the sun and my cock was semi erect, dangling thickly between my thighs. We passed through the naked sunbathers and began to stroll down the beach toward the surf. Andrea occasionally looked over her shoulder to see if any guys were following. However none were, and moreover there were no more nude sunbathers along the way. After 20 minutes walking we reached the open sea. We swam naked in the surf. Andrea emerged first and ran to a nearby copse of trees. I swiftly followed of course. Andrea had placed her arms around a tree, her legs spread wide, her luscious backside presented at me. I did not need a second invitation. For the second time that day I entered her from behind and began to fuck her. Damn she was so wet and slippery inside and I found it so pleasurable to withdraw my erection and plunge it into her seething wet sex again and again. Andrea was rather loud in her orgasms. It was her first outdoor sex, and she was apparently enjoying it. We were that busy fucking in the great outdoors that neither of us spotted the stranger. I saw him first. He was naked and masturbating while he watched us. I was still thrusting deeply inside of Andrea. I beckoned to the stranger. He approached quite quickly then. To my dismay he was much older, a bear of a man, maybe 50 years old and covered in body hair. He had a pot belly as well. Not our type at all. But my gaze was drawn to his erect cock.