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.