Further confirmation
here, were any still required, that the aircraft ended up off the SW end of the runway. It quotes an employee who watched the aircraft sinking from the rooftop of the High Tide Hotel, which is just off the LH edge of fdr's photo (south of the red-roofed building):
As to how the aircraft ended up there, presumably once it's hauled out of the lagoon we'll be able to see if it has reversers deployed, which would support the overrun theory.