A few days after my relationship with my first girlfriend became sexual, we participated in a 5K charity road race. When we got back to my place, she jumped in the shower. I (pleasantly) surprised her by joining her, and because it was my first ever coed shower, I was hard as a rock in a second or two. We 'cleaned each other up' real good, my dick getting a very soapy 'scrubbing'.
After we rinsed off and stepped out of the shower to dry off, I just couldn't take it anymore and bent her over the sink and entered her from behind. I was so horny I didn't stop to get a condom, or move into the bed. Just enjoyed my first ever bareback fuck, finally pulling out to cum all over her back and ass. We cleaned up again, and spent the rest of the day in bed.
Many times after that we would return from some kind of physical activity and hit the bed before hitting the showers. Must be something to that!