Bathysphere

The surface of this small black pearl shimmers with an oily iridescence. You harvested the perfectly spherical object from the corporeal remains of an aboleth - a sinister origin indeed.

You may speak the command word - "Wax on." - to have the pearl generate a sphere of invisible force which harmlessly displaces water or in a 5 foot radius, filling it with breathable air. Speaking a second command word - "Wax off." - ends the effect.