Look around for the chest's possible owner
From Create Your Own Story
Lord Frederigo had heard of such things before, this floating of chests upon underground rivers. His clan, the D'Honaires had fought the dragon for the past seven generations. His father was hero of the last skirmish with the beast. As a child, he had been regaled with tales of his fathers journey, and the many strange sights he had seen.
Once, in caverns ruled by the dragon's minions, his father had encountered a curious situation. A group of mercenaries, evading the patrols of those who served the dragon, had been smuggling items through the caverns, right underneath the dragon's nose!
Evidently, none had caught them, even to this very day. Frederigo glanced about, trying to find one of the smugglers. Though they were well hidden, they were rarely far from their goods.