Archaeia is a world surrounded by broken layer of Aqua.
'Natural' water sources on the planet are not common; most of the time, water sources for settlements are produced through magical means.
The Aqua floats well above the land, and occasionally people catch glimpse of Passing Aquas: floating bodies of water that peacefully pass by... usually.
At times, the Aqua has been known to grow unstable from its position in the sky and crash onto the land with devastating results if a Lapia Oak is not nearby to soak it up. This is known as an Aquafall.
It doesn't rain in Archaeia, but it Aquafalls...
Here be a copy of the murals seen by the party members in Chapter Five, while going through the Preservation Passage.
If you want a proper history lesson on the world of Archaeia - starting from the origin of everything! - then Cain does a better job than I can. (Just click the link above to jump to the relevant page in Chapter Five.) However, please find below a clean record of the murals for your perusal.