well i already told this story in another thread but i think it applies here:
some of my friends and I went vacationing in europe a while ago and visited this nude beach. well our group split off and my friend, girl i've known since high school, was walking to the beach nude with me. more as a gag than anything else but a little awkwerd nevertheless.
anyway, we were on the outskirts of the beach in the forest path and heard this bitch having the orgasm of her life. chuckling to ourselves we snuck over and got a closer look: only to discover it was 2 girls riding their boyfriends.
we stopped to watch for a minute shaking with laughter when i looked down and realized i had an erection. i was pretty emberassd so i just pointed @ it jokingly saying "look what happened now." then she GRABBED it and made it spring up and down!! she just giggled and called me a horny basterd. then we walked off to the beach and it wore off. (i have to say i'm kinda glad she saw it hard, i'm much more of a grower than a shower haha)
