When I was 19, I worked in a gravel quarry. As the excavation was moved around (presumably because the gravel deposit they'd been working on had played out), the holes they'd dug would fill with water. All the quarry employees used these as swimming pools during the summer, and I wanted to as well.
As I said, I worked at the quarry and not for the quarry. The details aren't important to the story, so I won't go into them here. Suffice it to say that I was able to see all these people managing to stay cool on even the hottest and muggiest days the Midwestern summer could throw at them, and I wanted to join in. However, I didn't want to do anything to jeopardize my job, so I continued to watch and wish.
My job kept me in the quarry until after midnight, and I began trying to come up with a way to make this work to my benefit. Then one day I got my chance. The day had been so hot and humid that it was still very uncomfortable at midnight, enough so I decided my time had arrived.
As soon as my day's duties were done, I started on my drive home. However, unlike every other night, I stopped at the nearest swimmin' hole. Since I hadn't planned this before I'd left for work that day, I had no shorts. No problem. It seemed like a perfect night for some skinny dipping, so off came my clothes, which I left in my car, and then headed for the water.
I swam around a bit, enjoying the feeling of the cool water, as my dick started responding by beginning to stiffen. I'd heard it said that some guys were able to get off by humping mud, so I gave it a go. It turned out to be quite a disappointment, regardless of anyone else's experience.
By that time, I was sorely (literally and figuratively) in need of relief, so I fell back on that old tried-and-true remedy which had served me without fail since the seventh grade. This time I didn't start out slowly and slowly ramp up the intensity of my jacking. This time my mission was to bring the relief which only a good, hard ejaculation can provide as quickly as possible. So I immediately jammed my jacking into high gear, stirring up the water as I slammed my fist up and down my cock as quickly as I could.
When I got that familiar feeling as my nuts let loose and my cum started on its furious dash toward the end of my cock, I felt absolutely wonderful as my orgasm delivered its promised relief. But I never got to enjoy the sight of my jizz floating on the water's surface. I found I might have brought on too much of a good thing. I was out in one of the deeper areas of this particular pool, and suddenly relaxing is not the best way to stay afloat. I was able to get myself a bit closer to shore, but I found my legs nearly unable to support my weight. Just when I thought I was going under for the last time, I discovered I was now in water shallow enough that I was able to sit on the ground and rest until my strength returned. I then went back to my car, got dressed, and headed home.
I continued with my midnight dips for the rest of the summer, each of which included a good, hard jack-off session. But I never jacked off again while in deep water. Drowning could have spoiled my summer!