The attached pic is while the pool was empty (grubby fingers included for size perspective). This is in the pool wall, on the opposite side of the pool from the IG skimmer, about 12-16" below the deck. There's nothing in the deck immediately above where this is, though the leveler is about 2' away. I have no idea what it is.
Also, probably a dumb question, but while the pic is there... That pool wall is plaster, right? Is that a certain type of finish? I read somewhere that Shasta had some sort of "Shasta Sand" and quartz finishes... Not 100% positive what this is and/or if there's any special care required for it.