Aqua (アクア, Akua) is the place that was originally Mars which was renamed after being terraformed into a habitable planet covered in oceans around 150 years beforehand. After the two ice caps melted, it became a water planet.
Aqua takes 687 Earth days to orbit the sun, about twice as long as that on Manhome. The calendar of Aqua is split into 24 months, and seasons transition very slowly. Man-made stations float in the sky to maintain a better atmosphere, and underground stations provide extra artificial gravity. Some nights are illuminated by the two moons of Aqua, one of which is very close and dominates the night sky.