Brief (three volumes so far) manga series by Kishiro Yukito, the creator of ''{{Gunnm}}'', following the adventures of a young knight-in-training on the watery world of Marmundo.

While traveling on her quest to become a true knight, young Ruliya is caught in a storm and sinks to the bottom of the sea. Her [[{{Magitek}} scuba-like armor]] keeps her alive, but the buffetting leaves her unconscious. Luckily she sinks near the shores of Lighthouse Island, home to Arrabarus and his young son Ashika. The island takes its name from the lighthouse powered by a strange, glowing sphere which may or may not be the spirit of Niselle, Arrabarus' dead wife.

Shortly after Ruilya's arrival, more visitors come to the island: MadScientist Alcantara and his minions Zycrow and Zykey. Believing the sphere to be the final ingredient for the Elixir of Life, Alcantara steals it, destroying the lighthouse and badly wounding Arrabarus. The intruders set off, with Ashika captive aboard their flying fortress and Ruliya following close behind. On her quest to rescue Ashika, she crosses paths (and swords) with various monsters and demons, and makes a rather... [[TheGrimReaper unusual friend]].

First published in 1998, ''Aqua Knight'' is currently "on hiatus" according to Kishiro. Originally the story was a way for him to take a break from writing ''{{Gunnm}}''; when he continued that series with the ''Last Order'' books, ''Aqua Knight'' was set aside again. A lighthearted adventure with just enough drama to keep things interesting, the story is wholly different from the dense cyberpunk world of Gally and Ido, but no less enjoyable for it.
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!!Contains examples of:
* AbusiveParents: Ruliya's flashbacks in volume 2 reveal that her mother was a big time {{Jerkass}} who let Ruliya be bullied and often complained that her daughter wasn't as strong as her and Ruliya's dad.
* ActionGirl: Ruliya
* AGodAmI
* AuthorAppeal: Explanatory diagrams, sexy badass fighters, over-the-top facial expressions and science [[ForScience WITHOUT LIMITS!]]
* BoisterousBruiser
* CollapsingLair: Castle Zondac
* {{Expy}}: Ruliya looks an awful lot like a grown-up Koyomi, whilst Alacantra's friend Augustus ''is'' Doc Ido.
* FairyCompanion: Pinoque, to Ruliya
* FlatEarthAtheist: Alacantra counts doubly - not only is he atheist in a world where gods appear regularly, [[spoiler:he also lives on a flat world]].
* ForScience: Of the "natural philosophy" kind.
* GentleGiant: Gygro.
* {{Gonk}}: Zycrow
* TheGrimReaper: Tagmec
* IllGirl: Zykey
* LoadBearingBoss: Lord Basso; after Ruliya defeats him, Castle Zondac crumbles into the sea.
* LowFantasy: Cut from the same cloth as ''Film/{{The Adventures of Baron Munchausen}}'''s tales. It's loaded with foreshadowing and potential arcs though, and, had it run any longer, might have expanded into HighFantasy.
* {{MacGuffin}}: "Niselle"
* MadScientist
* {{Magitek}}: Alcantara's inventions and the Aqua Knights' armor
* TheObiWan: Arrabarus, briefly, to Ruliya
* OnlySixFaces: Not that few, but you will recognise Kishiro's reuse of face types if you have read his other works. And it goes both ways: Zycrow later gets wholesale transplanted into the Last Order as a Tzykrow, Gally's JerkAss Panzer Kunst teacher.
* PlanetOfHats: Zygote, land of precision and science
* PetTheDog
* ThePromise
* [[RedheadedHero Redheaded Heroine]]
* RobotGirl: [[spoiler:Zykey; Alcantara built her a clockwork body to replace her own vanishing flesh.]]
* SwordFight
* TalkingAnimal: Zuma the Blue Cat
* TalkingTheMonsterToDeath - Unusually, used by a villain
* VerbalTic: Tagmec, who has a habit of randomly ending his sentences with "Bone."
* VillainSong: Alcantara gets a really good one.
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