When dust said we were going to a lake in a rock quarry, I presumed he meant a quarry that was disused and abandoned. You know, like you see in kill scenes of dour TV shows and such. Nope, not quite. As we pulled up, I found that we were actually entering the lake area through the entrance of a real, in-use quarry. You know, like you see in kill scenes of dour TV shows and such. (Wait, did I just say that?)
Anyway, as we passed through the mounds of rock and dirt, heavy machinery, industrial buildings and whatnot, we found ourselves at a huge lake whose shoreline was filled with what had to be thousands of people. Cranes and diggers and whatever else you call them were in the water, being used on the weekend as a playground for many a daring thrill-seeker. (This video on YouTube at a similar lake is a good example.) I have no idea if the machinery in the water is still used, but it seems like it probably is.
In any case, this place was a trip. We found ourselves a tree-shaded area on the opposite side of the lake, and proceeded to lounge and swim. And I can assure you: The water really is that clear and that blue.