When I was a freshman in college in Arizona, I went on a short "rock climbing" trip, nothing that strenuous or requiring equipment or particular experience, just clambering over large rocks on a warm and sunny, but not scorching day.

We were told to bring water, but I only took a small water bottle, and it didn't last that long. I was kind of shocked when my vision just went all blank and red with some random sparkles. One moment I could see, the next I was fully conscious but blinded. I wasn't that far away from other people, but I wasn't right next to anyone. Luckily I wasn't that far from rocks that provided shadow where I could get out of the sun, but I was afraid that by doing so, I would be hiding from anyone who could find me. And briefly I had no idea if my condition was permanent, I was going to die, or what.

Anyway, I wasn't a European or city dweller, just a clueless kid not used to the desert and/or outdoor activities much.

I think a lot of people do dumb things, and some survive and learn, and some don't.