When I was 15, I swam for the local swim club. The pool was two miles from my house, in the middle of a farm field. I was too young to drive and my parents were too busy to take me to practice, so I usually rode my bike.
After practice, I would get on my bike, wearing only my black Speedo briefs. The road home had light traffic and ran through farm fields filled with corn and hay ready to be harvested. The combination of the heavy smell of the crops and the hot sun beating down on my nearly naked body made me very horny, as I rode slowly home, my cock, which was very thick for my age, got hard. This was almost as soon as I started to ride. The head of my cock peeked out of the waistband of my bathing suit, as my balls rubbed against the seat of my bike. I slid forward and back on the seat, letting it massage the swollen area between my anus and my scrotum. I let the butt end of the seat press against my anus, and that made my cock pop out of my suit.
As I stood up on the pedals, I loosened the string in the waistband and let the front drop. I pulled the waistband under my balls. My cock jumped into the sunlight, just as a car drove by. The car did not slow down, so I knew they didn't see me, though I kind of wished they had.
I was so horny now and I decided to pull off into a little path near one of the fields. The smell of the earth and the vegetation was intoxicating. The heat of the sun made me want to pull off my pants and masturbate.
I laid my bike down and walked a little toward a fence. My cock, fully exposed, swayed from side to side as I walked. I pulled my briefs off completely and dragged the nylon fabric down my cock, under my balls and across my ass. I stood on my tiptoes and laid my balls and cock on the top rung of the wire fence, letting it press against the swollen flesh under my scrotum. By now, the pre-cum had drenched the glans of my cock and the little opening at the tip was gushing with more lubricant every second. As I worked my cock with both hands, I pressed my balls against the wire fence. and the sensation was overwhelming.
Just then, I heard a car drive up near the path and slow down. It seemed to stop just short of the path and I heard the car door open and shut. I could hear someone walking through the grass, so I had to come quickly, or be caught in the act. I could hold back no longer and looked down at the end of my cock as stream after stream of sperm shot into the air. It fell into the field, onto the fence and all over my hands. I rubbed as much as I could into my balls, my ass and my pubic hair.
I shuddered for what seemed to be a full minute, just as a stranger came into the path. In modesty, I held my briefs over my sperm-soaked ass and pretended that I had been peeing. I quickly put on my swimsuit and picked up my bike that I had laid next to me. The stranger looked at me, but said nothing. Then he glanced at the fence and the grass next to it, and I saw that he was looking at a large gob of white sperm that was hanging there. He looked back at me and smiled. I ran with my bike and rode home, thinking about the stranger and whether I would see him after my next swim practice.