My friends normally have a get together once a month where we drink smoke and play games. There are 5 couples including me and my girlfriend and we normally take turns hosting. We have been doing this for better than 4 years now and in all that time there has never been anything sexual or even talk of making our get togethers sexual. A few months ago one of our friends decided they were going to get a hot tub installed in their house. They ended up getting a pretty big one that comfortably seats 6 people. They were excited to show it off and asked if they could host the next get together. Naturally we all said yes and met at their house the next month. The night started out like any other, laughing and drinking like normal. We started to wind down the evening and and a few of the couples had already left for the night leaving just me, my girlfriend, and the couple who hosted the night. I was just about to ask my girlfriend if she was ready to leave when the other woman asked if we wanted to get back in the hot tub. My girlfriend accepted the offer and so we made our way back to the tub. We continued drinking and before long the conversation turned to s**. The other woman then asked my girlfriend if she could be honest with her. She then said that she had always thought I was hot and used to imagine what it was like to be my girlfriend and have s** with me. My girlfriend was shocked and asked her what her husband thought about her being so open and honest. That's when he spoke up and said that he knew all about it and was fine. He proceeded to then say he had imagined he was me and was f****** my girlfriend. I was still kind of at a lose for words when my girlfriend asked them if they wanted to swap partners. I couldn't believe what I was hearing, but still went along with it. Before I knew it, my friend was sitting next to me naked and my girlfriend was sitting next to him naked. One thing led to another and before long I was f****** our girl friend and my girlfriend was f****** our guy friend. After we finished, our girl friend asked if she could go home with me for the night while my girlfriend spent the night with her husband. We agreed and our girl friend ended up going home with me while my girlfriend stayed there. We f***** 4 different times before morning. Then we f***** again right before we left the house to swap wives back. We all agreed the evening was exciting and decided we should do it again. So now after everyone breaks for the evening after our get togethers, us 4 will swap wives for the remainder of the night. I'm not sure if f****** our girl friend is more exciting or knowing that my girlfriend is being f***** by our guy friend is.