In the base game, the edge-case where this can happen is if Bringer of Dreams and Nightmares uses Vengeance of the Dead (with threshold) on the Ocean itself. A Town/City/Dahan is moved to the Ocean, triggering Ocean In Play which Drowns it. Drowning (destroying) it triggers Vengeance of the Dead. If Bringer deals VotD's "damage" in an adjacent land to "destroy" a Town or Explorer and Push it into the Ocean, Ocean In Play can't trigger again, because actions can't trigger themselves, even indirectly. So the Town/Explorer isn't Drowned.