I turned 14 during a family summer holiday when all five of us stayed in a smallish caravan, by the sea. We were all quite private as a family and I particularly needed privacy, in view of what my body was doing, and what I was doing with my body. I needed to masturbate at least once every day and more often if the chances arose.
I can only clearly remember one of the orgasms I had on that holiday. I had been bathing in the sea, with my brother and sister, and afterwards we all had to change back in the caravan. My brother and sister did not seem to mind changing in the main body of the caravan, but I needed and wanted privacy, so opted to change in the small toilet closet. It was barely wide enough to stand in and undress/dress, with only a thin door and a high window overlooking the sea, and probably only four or five feet away from the rest of my family.
I had a towel and my underwear, shorts and shirt with me to change into. As I dropped my swimming costume, my prick was already stiffening and by the time I had, with difficulty, stepped out of the costume altogether, it was fully erect, in expectation of it's usual beating off. There was an immediate problem: my cock and balls were covered in bits of sand, sticking tightly to the skin all the way up and over the helmet (I am cut) and making it impossible just to wank as normal.
I needed to wank but also realized I could not be too long in the toilet without arousing comment. I usually produce a lot of precum but none had yet formed, so I dribbled as much saliva as I could over the helmet and started to ease off the sand particles, until it was more or less clear (though some still clung to the underside and inside the rim, I really wished I had a shower and some soap). Soon, with a reasonable area of exposed glans, I could work my prick with a finger and thumb and begin to feel the sensation rising in my thighs and groin.
It does not take long at 14 to bring yourself off. I had to be careful to be silent and also retain the sperm somewhere. I was too late to lift the toilet seat, with my clothes on it, and the toilet paper would rustle too loud if I grabbed some now. The flow started and my slit spat it out, I stooped and shot over my wet swimming costume, panting silently, watching the white pool soak into the wet fabric.
I recovered as soon as I could and dressed, stepping out into the caravan and an unsuspecting (?) family. I made a note then to make sure that the next time I put on the swimmers, the evidence of my teen wank would not be visible to all.