The shift of impressions about the Nautilus, from its heroic crew protecting the seas, to that vision of a desperate bunch of renegade people who carry the burden of an spiritual do-or-die battle to wipe the errors of their own past. That leaves a powerful sense of this series' scope and conflict represented beyond that actual human civilization of the time, but that reflects on the human nature.
The Neo-Atlanteans carrying a legacy, the Nautilus/New Nautilus as the opposing force, all of them committed to the same conflict since they landed on Earth, but now also perpetuated by the created humans. Following their origin's sin, dangerous ego and continuous misfortune. All that strikes what I find is a right balance between immobile fate and own-existence despair, and otherwise the troubled nature (to the point of being annoying) of Nadia and her sometimes tragic heroine stance would have fall flat.
