Listening to my wife on the phone planning a visit from her sister, I told her we should make it fun and have Elli and her husband skinny dip with us when they came down.
After hearing her say they agreed to it, the anticipation kept me horny for weeks. When the time finally came I knew it was worth it too, watching Elli get undressed and seeing fresh tits and a new pussy walking around the house naked.
Playing games in the pool I got to feel her tits and rub her pussy a couple of times while swimming between her legs. Once, she backed right into me with her naked ass and it felt like she fit perfectly against me. I was starting to want her badly.
Leaving the cold water of the pool and jumping in the jacuzzi to get warm, I got a beautiful view of Elli's pussy from behind as she climbed up the step to get in, bending down to brace herself then spreading her legs to carefully locate a seat to stand on with her foot. I got close enough I swear I could smell her pussy.
Later, after a small banquet of food and drinks we all headed back to the pool, I think we could have kept this up all night we were enjoying ourselves so much.
About an hour after warming up in the jacuzzi a second time, my wife got up and went back into the pool to cool off again, Elli's husband followed her.
Elli's naked ass bobbing up and down to the waves in the jacuzzi had my cock so hard I thought I would burst. We sat making small talk as her husband and my wife remained outside in the pool chatting quietly.
Seeking an opportunity I said to Elli "you know they are fucking, right? I can see them from here, her legs are wrapped around him and she's making her face, I know that face."
"They aren't fucking, Shaun, if you want to fuck me just ask, no reason to make up stories."
"Okay" I said, "I want to fuck you"
"I bet you do! she said, laughing. "If it's my ass that's making you so horny why don't you just jerk off to it, I don't mind that, but I won't screw around on my husband."
"Sure, they are out there fucking and I get to jerk off. Great, thanks a lot"
She said nothing.
I moved behind her and laid my cock on her wet, slippery ass and slid it back and forth a couple of times.
She took another sip of her drink.
I continued sliding it back and forth, moaning as I watched the head of my cock barely catch the tip of her perky asshole and then continue on upwards.
"Hurry up" she said "I wanna go get another drink"
"I'm fantasizing about fucking you in the ass and it's really turning me on, it won't be long now."
Again, she laughed.
I pretended to lose my footing in the jacuzzi and I fell down on her, grabbing around for her tits and forcing my cock hard against her hoping my cock would find it's own way, it didn't.
"Fuckin' jerk get off of me, I'm going to get a drink."
I grinned and went and got another drink for myself, making a stop at bathroom I grabbed a container of Vaseline and a clean towel.
Stepping back into the water and seeing her perfectly trimmed bush floating and her legs spread was almost more than I could stand.
"Stay on your side of the jacuzzi" she said, practically snarling.
A few minutes later she was back on her stomach, sipping her drink and bobbing up and down right in front of me again. That perfect ass glistening in the light.
"One more try, I won't fuck it up this time"
"No! keep your dick to yourself"
"Whatever, why don't you want to fuck?"
"I've never screwed around on him and I'm not about to start now"
"But he can fuck her out in the pool and that's okay with you?"
"They aren't fucking they are just talking"
"I already told you I watched them fucking and Jan never lies to me, she'll tell me tomorrow that I was right and we will be missing out on good sex"
"Man, you really want to put your dick in me don't you?" she said, stirring her drink.
"What have I been saying for the last hour? Come sit on my lap and slide down onto me and cum all over me, what's the big deal?"
"I can't anyway, you could get me pregnant."
"Ugh, fine. I'm gonna jerk off onto your ass then"
"Shaun, if you get near my pussy I'm gonna break this glass over your thick skull."
"You got it."
Unfolding the towel and grabbing the Vaseline, I slathered it on my cock...vowing to fuck this little cock-tease.
Jerking-off against her ass I began rimming her tight, puckering asshole with the head of my cock and moaning like I was about to blow my load.
"Shaun, leave my ass outta this and hurry up, I need another drink"
"I'm, I'm almost there" I said moaning
Watching the head of my cock disappear into her asshole made me almost cum.
"Shaun!" she yelled, as I fell on her, this time with my full weight.
My left hand grasping her mouth, my right grabbing her tits and finding a nipple to pinch hard. I spread her legs with my feet, wrapping them around and under her, forcing her legs apart I pressed my cock a little deeper.
"mhm mhm!" she mumbled.
Damn, I thought...I'm in! For an hour I begged, now she's gonna feel it.
Her legs stiffened, squeezing her ass cheeks as tight as she could, she continued to struggle as I held my position and played with her soft breast. Finally her legs relaxed just for a second and as her ass began trying not to relax her hand came back and she dug her nails into my thigh as if to say "Don't you dare!"
Right then her ass loosened up completely and I gave it everything I had and thrust in another inch and a half or so, she let out a squeak and tried to tighten back up.
Carefully sliding my cock in and back out a little at a time to get a motion going, I slid my hand from her breast down her soft skin until I found her steamy, soaking bush. I began tweaking her clit to force her ass back onto my thick, seven inch cock. It worked like a charm. After three full minutes of her kicking and scratching to get away I was in deep, my right hand now flicking her clit like mad.
Thrusting with all the energy I had into her ass, which was now starting to open up for me, her body went limp...she finally came for me.
She began to whimper and it was more than I could take. Oh Elli, baby. Fuck! I moaned, slamming all the way into her now that she was prone and weeping. I started fucking her like I had wanted to do all night. Leaning back on my feet I grabbed her hips and held on tight, fucking the shit out her limp body now that she was mine.
Just as I got a rhythm going I glanced up to see my wife standing there. I'm pretty sure what it must've looked like to her with her sister just lying there letting me fuck her, all I could do was grin. My wife smiled and gave me a wink before turning back for the pool.
Still grinning I unloaded into Elli, filling up one of the finest asses I'd ever seen, I held her tight against me pumping every bit of cum I had into her.
My wife later told me that she rode her brother-in-law's eight inch cock out in the swimming pool and had three outstanding orgasms. Asking me if I enjoyed myself with her sister I simply said "Yea, it was alright". She replied "Mhmmm".