I used to work as a lifeguard at a theme park.
It was mid July, and it was ~100 degrees outside. Not a cloud in the sky. It was hot for me, wearing a set of khaki shorts and a thick polo shirt. I had the break guards go on water runs as needed, and guards were permitted to rotate by swimming in the pool. This was to keep them happy, and to keep them from dropping like flies in the deathly summer heat.
At our park, we had a slide that was about 60 feet high. This slide had three channeled slides that started off like a pipe, and then became fluted (half of a pipe, no upper half) channels. One pipe, and the most popular, was the one slide that went down at an 80 degree angle. It was completely open. You sat down, and slid down the 60 feet within two seconds. Quite a thrill really, if not a quick one. Two guards manned the ride, one at the bottom and one at the top, to control the antics of the guests at all times.
As midday comes around, I settle into the usual rhythm. Bored, I begin watching the sliders go down. Four people come every 15 seconds, like clockwork, as they should.
At the top, I notice one of the guards turn around as a teenage male prepares to get into the slide. This is a problem. Teenage males are the trolls of the park, their antics a perpetual source of problems. Then I see the kid take two steps backwards. I know what he is about to do. He must be stopped. But, alas, what am I to do? I have no way to contact the lifeguard up top. There is no phone, no radio. I blow my whistle twice.
The kid ran and jumped clean off of the slide. Now, up to this point in my life, I had been afraid of things. Getting in trouble at school, failing something miserably. They all made me a tad anxious. A lot of things had made me scared, and a lot of things had made my stomach churn. But nothing, in all of my life, had made this scared until now. Seeing a young man fall to his impending doom and being powerless over it makes you feel terrible. Feeling, by some extension of logic, that you are indirectly responsible for this, makes it even worse. Never, in my life, has my stomach and jaw dropped so fast.
To his credit, the jumper assumed the proper position of arms and legs being crossed. But now he was clean in the air, flying like a lead brick. As he did so, his body turned ever so slightly. It was something he noticed, and fruitlessly tried to correct. Instead, he fell some distance before hitting inside the flume and chaotically tumbling down the ride.
I called the paramedics immediately, and we had to backboard this kid out of the splashdown flume.