Compare the foreground box beam in the third image above, to the beam at Arrow 2 in image six of my post 45 of this thread, shape only.
If it was black before the collapse, and black while still in the water right after the collapse, why is it green, and a sloppy job of green to boot, now?
I think the visible surfaces in the 3rd image are exactly what we are looking at in the 2nd image, i.e. the inside of west U10. Note the little scar along the edge of the horizontal top piece.