TL;DR Before the City of Naho, their people lived underwater thanks to powered masks that gave them the ability to breathe underwater. After their powered masks are taken to the vaults, they are forced to live on the surface of the water. In the present time of the story, Gali will be able to rediscover crippled underwater remains of the original city all over the seabed. Could serve a story purpose, or just make for some cool backdrops and lore.
I’ve been a long time lurker, but coming right off the last TTV podcast, an idea has been itching in my mind. Naho has a lot of potential in settings, the current one being a seabound port, as described in Gali’s character bio. A lot of really cool concepts and ideas for Naho were floating about early on, but ultimately a lot had to be scrapped so there weren’t three different cities Gali would be having to juggle.
With the introduction of the vaults, it opens up some potential in how it affected the matoran and their way of life before and after their powered masks were taken. The people of Naho in my mind are perfect for exploiting the potential of this. I am not sure how much of a stretch masks of water breathing are as far as physical augmentations, but I don’t see too much of a power creep stirring from it. If masks of water breathing are considered fine, then it opens up a lot of potential on where the people of Naho lived prior.
The masks of water breathing allowed them to be completely independent of the surface world. Hydruka can be taken from G1 so they can make air bubbles. The matoran could then have created dome structures and fill it with said air so they have space they can audibly communicate with one another. Underwater caverns with the air is a possibility too.
There are also reasons for even bothering to live underwater beyond how cool it would be. An isolated location difficult for their at-the-time potential enemies from other matoran settlements to strike them. It is the best way to attune themselves to their element as well, to be in it 24/7.
After their mask powers are taken though, they would surely perish if any of their air-filled structures or caverns suffered structural damage. And so, they were forced to leave their home behind and live above sea level, prior to the Toa getting the masks in the vault. After such a long time has passed with so much forgotten or dismissed as fairy tales, the knowledge of their old home would be lost.
This serves a potential purpose to the story later on, as a bunch of writings and history would be found bellow, just waiting for Gali to learn about and reveal more about the past of their civilization. This can be as little or as much as pleased, depending on how much damage it is decided they suffered after being abandoned.