On the "water planet" AQUA, which was transformed by humans, there is a famous tourist city "New Venice". The 15-year-old Mizuno Tomo (voiced by Erina Hazuki) came to New Venice from Earth, dreaming of becoming a handsome navigator. The main job of the "navigator" is to row a gondola to take tourists to appreciate the beauty of the water city. She works as a navigator in a navigation company called Aria. She has met friends such as Lanhua and Alice, and also met Alicia, who is known as one of the "three major water elves". As a "half-experienced" Tomo, although she cannot sail and entertain guests skillfully, she works hard for her dream every day. In the water city New Venice, the optimistic Tomo and her friends experience all kinds of new things. From these encounters that are completely different from the earth, Tomo gradually realizes what it means to be an excellent navigator.