Anime!

It’ll be so much easier if you lazybones have read the manga so I don’t have to explain it all, but I guess it can’t be helped; an undine is the gondolier in Mars. Due to terraforming mistakes, the whole place is covered with water, giving it a global, Venice-like environment. Therefore, undines are a group of people who will ferry people and good across the waterways, while at the same time acting as guides. End of background explanation.