I haven't started looking at the actual technology of the Nautilus yet - I'm currently looking at getting the right blend of cramping and claustrophobia and grand architectural vision. I've been referring to mansions and cathedrals as well as submarines, hence the absurd doorway and high, vaulted ceiling. I want the interior of the submarine to be quite unsettling, both beautiful and disturbing, so lighting from below = instant eeriness. I saw one of those chandeliers with spherical bulbs and loved it, but it seemed ungainly hanging from the ceiling, so it was relegated to the floor, with the added bonus of unusual lighting.
And some kelp, with dramatic lighting. You may have noticed that I love dramatic lighting, so this is definitely an angle I intend to investigate further. Again, very simple and loose, just a very quick study.