The Gungans have a dry city underwater, which keeps the water at bay via force fields that block water, but not people entering them.
This struck me as odd, as I wouldn't think they'd evolve to be an underwater species that would need dry/open air living space.
So, where did the Gungans develop as a race/species, and how did they acquire the tech necessary for Gungan City?
Any canon that addresses this question is fine, as I don't expect it to be covered by the current Disney Master Canon.
This is largely covered in the Phantom Menace Visual Dictionary.
In short, the Gungans evolved in the Naboo swamps, where most of them currently reside. After their planet was contacted and colonised by the Naboobian humans, the Gungans began to trade plasma, food and various manufactured products with the Naboo. This "borrowed tech", along with their own R&D (mostly focusing on on 'grown' technology like their Bongo Submarines and Hydrostatic Bubbles) have allowed them to move large segments of their civilisation underwater.
GUNGANS EVOLVED in the swamps of Naboo, becoming almost equally well adapted to life on land and in water. The amphibious beings live in underwater cities hidden in deep lakes, breathing air or water with their compound lungs. Secret techniques allow Gungans to 'grow' the basic structures of buildings and vehicles, which are complemented and finished by Gungan artisans in organic styles. Gungans trade with the Naboo for certain items of technology, but manufacture everything else they need from the resources of their underwater habitat. Although Gungans use mechanized vehicles, they have a close affinity with the natural world and still prefer to utilize living mounts and beasts of burden.
