Several years ago, this unplanned experience with a friend's wife and their 18 y/o daughter was so hot and unforgettable, it is still the visual in my head that can get me instantly hard.
I had pulled my boat and trailer in front of my friend's house after a long, hot day on the water. The neighborhood couples were meeting there for a cookout. Climbing out of my truck, I decided to get in my bass boat and stow my fishing rods and tackle. As I sat sideways on one side of my boat working on sorting tackle, my neighbor's daughter approached from the side I was facing. After a short time, I noticed her eyes glancing toward my crotch. I had my sunglasses on and glanced down, immediately noticing a large gap in the left leg of my shorts. Since I had on loose boxers, I knew she was getting a serious peek at my hanging balls, if not more, from just 3 feet away. The height of my boat and where I was sitting was just below her eye level from where she stood.
Thinking quickly, I asked if she would grab me a cold bottle of water from the house, as I was going to be in the boat another 15 minutes or so. She agreed. As soon as she left, I began to fluff up, which was easy, as I was quite excited by this lucky encounter. I made sure that my entire package was outside of the left leg of my boxers and set my shorts so that the gap would be at its max should I "inadvertently" open my legs while reaching for something. I was all set.
She returned and went right back to where she had been, directly in front of my left leg shorts gap. As I reached for the bottle, I felt the gap open and knew I was fully exposed. Casually I leaned back and took a big swig, legs open for balance. As I did this, she crossed her arms, leaned down to rest them on the side of the boat, then rested her chin on her arms, now perfectly eye-level with my gaping shorts. I guess she was mesmerized by what she was looking at...she locked her eyes on my cock and her gaze never wavered.
I'm certain she wasn't experienced with guys, being more of a geeky, withdrawn, bookworm type that didn't get invited on dates or go anywhere socially. This was likely her first clear look at a real, man-sized cock, in the flesh...and at very close range. Peering through my glasses while pretending to mess with fishing stuff, I could feel the air and her eyes on my dangling cock...then it started to grow. She never looked away or changed her stance, she was locked in. In short order I was super swollen, but still dangling, and not letting on that I noticed her gaze.