My friends girlfriend

One of my closest friends is in an open relationship with a blonde blue eyed beauty, she looks like Marilyn Monroe with a nose ring. My friend is a really nice, good person but physically he is short and scrawny, with a small penis. Even though I love my friend to death my fantasy is to dominate him and have sex with his girlfriend in front of his eyes. I'm about the same height, a few inches taller but I'm a lot more muscular and have a large girthy cock. My fantasy is that all three of us would take a hike together in the wild and we would set camp close to a lake, where we would swim. The flirting between me and the girl would intensify slowly throughout the day, as would my friends discomfort with it. When I take of my clothes to swim I suggest that we skinny dip, which she agrees happily to, and my friend agrees grudgingly to. When we take of our clothes she sees my naked body and compares my more muscled masculine body and larger cock to her boyfriends smaller feminine frame and boyish penis. She and I begin to make out while her boyfriend looks on helplessly. I switch between fucking her ruthlessly and romantically in many positions until I end it with cumming deep inside her pussy during doggy style. All this time we ridicule and laugh at her boyfriend.