On many occasions during sex my wife and I have wound up laughing hysterically... because of a really loud squelching noise, or because one of us said something really funny while trying to talk dirty
I love the way a good laugh makes her vagina squeeze and pulsate (Sorry, honey
Couldn't think of a better way to describe it).
Sex is funny sometimes. It's good to be relaxed enough with someone to laugh about it; but it's not always easy to be that secure.