Aria The Animation, and its sequels Aria The Natural, Aria the OVA ~Arietta~, and Aria the Origination are a set of series which original manga was written by Amano Kozue (天野こずえ).
It has quite a peculiar genre, which is utopian science fantasy.
Originally entitled Aqua, this series was aired from October 2005 to March 2008, and it is really refreshing to watch.
On the planet Aqua lies the watery city of Neo Venezia, a tourist hub in which people travel around in gondolas. Professional gondoliers known as Undines are well-revered as they act as tour guides for the people.