>>18 Ok, I read the first two manga volumes.
The planet is called Aqua, it's Mars terraformed. The poles melted beyond expectations and so the city ended underwater.
The wind farm is located elsewhere.
Motored gondolas exist.
Tides exist.
In the manga they are several small moons in the sky, not one big Earth-like moon like in the anime.

No near collision with a spaceship/airship ITM (in the manga.)
No annoying phone call from an irritated man ITM.
The girls are busy ITM. No annoying kid ITM. The anime skipped the whole Aria (the mascot) magical encounter and added emo stuff.
The anime didn't impress overmuch; the manga is a wow experience, one gets deeply involved with the characters, plus there are some very breathtaking moments.
Hopefully future anime episodes will catch up to the manga.