just went "wading" in one yesterday.Most, if not all, of these are pits where clay or sand was mined. I don't know the precise reason for the bright blue color, but it has to do with light absorption and the minerals in the water. Certainly you can visit any that are on public land. Color-wise you'll find that the effect dissipates as you get close, and is most striking in aerial photos. Other than that, they are not always the most scenic nor the most interesting locations in the woods, but some are more interesting than others.
I will carefully consider your Wreckreation Hypothesis!I have always firmly held the belief that the color comes from all the abandoned blue cars and trucks that sit at the bottom of these sand mines and clay pits!!
That’s my story and I’m stickin’ to it!