Well, in my experience with these things(kink, not swinging), the women tend to be a bit stand-offish at first. You know... Yes, we are all there for a reason, but we are people, too. If you see a woman that you think is attractive, just start up a conversation with her, and see where it goes.
I mean, I doubt that you're approaching anyone in a rude manner. But men at these functions often times forget that there is a woman behind the boobs and vagina. All decency is just thrown out the window for a lot of them. So when someone approaches me like I am an actual human, it gets them much further.