Aqua

After 150 years of Terraforming, Aqua, the formerly planet known as Mars, now has more than 90 percent of its surface covered in water. A young girl named Akari Mizunashi arrives at the city of Neo-Venezia, an exact replica of the old Italian city of Venice, hoping to become an Undine, the most coveted job on Aqua.

(Source: Tokyopop)

Note: Includes one extra chapter.