Sitting in the hot sun, dehydrating, not drinking enough water - it can happen to anyone. If you are drinking any kind of alcoholic beverage, it dehydrates you further.
And therein lies the problem - many people go out in the hot sun and then get thirsty. What better way to quench your thirst at the beach than with a cold beer, or a wine spritzer, or a margarita? So many people do it. We had friends in Pompano Beach who would go out on their boat with suitcases of lite beer, iced down in a cooler the size of a child's coffin. They drank prodigious amounts of the stuff, all day long, in the hot sun, apparently without ill effect.
Apparently. The problem with alcoholic beverages is that your body wants to expel the poison that is alcohol, so the kidneys go to work filtering all that out - along with a lot of water - and after a beer or two, you have to go pee. So you go and now you are dehydrated and thirsty and you think, "Gee, I'll have another beer!" and the process repeats.
We met a guy at one campground who told us his theory of beer drinking: hold it in. He said that if you do that, eventually the urge to pee goes away and you don't become dehydrated. "Once you open the drain plug," he said, "you'll be peeing all night!" I am not sure this is sound medical advice. Sounds more like a sure-fire way to get a kidney stone. Maybe that is why people from dry climates get them - they are holding it in.
A better approach is to not try to hydrate with alcohol, but try water instead. Stay out of the sun (use sunscreen anyway), and don't stay out in the heat for more than a half-hour to an hour at a time.