You get awkwardly close to the guards and do your best to peek inside the slotted crystalline chest. You see the orange Eternity Orb floating against a cradling divot in the ceiling. At first, it looks much as it always has.
Then you notice a small rocking movement coming from the Orb. You've never noticed it rocking like that before; the chest is specially carved to house the Orb, so it should be a perfect fit. Maybe it's reacting to a strong current from all the gawkers. Maybe it was damaged in the rescue. Or maybe it's rocking because it's not the original.
You look back at the crowd of merfolk coming and going. Nobody else seems upset by this, and even the guards are starting to give you funny looks. Maybe you're just being paranoid. Maybe everyone else is just too eager to be complacent.