Google shows a little stretch of road as South Fork 41364. Just north of the main drag, there's a little side road identified as Griffith Cemetary Road. If you follow that up a bit, you see a small body of water (kind of trapezoid-shaped), and at the top of that body is what looks to be a rock formation, not unlike the rock the boys are using as a diving platform. Don't know what it looks like from the ground, but from the air ... it looks to be lush gorgeous country, still the perfect setting for a swimming hole!

this isn't Saturday bath day so they can go into town?

It may have been on a coal mine tailings or be downstream of the outhouse even at the time. Standards for sanitation and/or safety were not high, and no one would really think twice about swimming in farm ponds or random watering holes, and didn't spend a lot of time neurosing about what might be in them. More generally, people were not nearly as fearful of everyone and everything - that's an unreasoning modern affectation, coming in a western world that is almost obscenely safe, wealthy, and comfortable for 3-4 generations.

Lacking but the overhanging tree bough with rope swing attached to be a real piece of American "good old days" imagery.

One wonders -- is this swimming hole now clogged with coal tailings or has it succumbed to concrete as the result of a flood control project? If not, fear of flesh-eating bacteria or toxic algae may still limit its modern-day clientele.

What the germ count is in that puddle? No blue flag for this body of water, I would guess.