You send vibrations from your body into the ground, or a solid surface you touch such as a wall. The vibrations travel through all solid material and inform you of the presence of every Medium or larger creature and object within the spell’s area. Creatures not in contact with a solid surface, such as those that swim or float, cannot be detected by this spell.   A creature within the spell’s area detects the vibrations if it has a passive Perception equal to or higher than your spell save DC, or if it has the Tremorsense feature. A creature with a passive Perception that exceeds your spell save DC by at least 5 knows the general direction of the spell’s origin.