One of the interesting elements of Gargantia is the sci-fi anime's often subtle attention to details. We saw this again in the latest episode with a map of the world that reflects real topology.
A new fan comparison
Also of note, new submarine remains designs from official site
Speaking of mapping, Ledo's tanning over the course of the series...
For a bit more Gargantia fun, an early look at the store specific illustration bonuses, offered with the Japanese Blu-ray release.