Upon triggering, all characters within the affected area are levitated a few feet off the floor. They have no control over this effect, nor does anyone else in the party. Levitating characters will simply hover in the air, unable to propel themselves.
Unless the characters can grapple a solid surface and pull themselves along, are themselves pulled along by someone else, or are able to use some sort of magic (another levitation spell, flying, etc.), the characters are stuck.
The effect will last until a successful Dispel Magic is performed, or until the characters leave the dungeon.