Funny/Embarrassing Nude Beach Story

me and my girl friend went to a nude beach once with some friends, she told me she invited one of her friend who wanted to learn/try out being a nudest, well when my GF introduced us I couldn't help but notice how good her friend looked, and then right there in front of everone I got an erection, I was so embarrassed, I still can't see her friend without thinking about that horrible moment