- Nadia la Arwall
- Nadia is a 14 year-old Kenyan circus performer. She is stubborn, short tempered and a strict vegetarian. After Jean rescues her from the Grandis Gang, she sets out on an adventure with him to determine the origin of the "Blue Water", the jewel that beckons the criminals to her. Always accompanied by her tamed lion cub, King, she sometimes mistreats people, but as she grows closer to Jean she learns to become a much more caring and trusting person.
- Voiced by: Yoshino Takamori (Japanese), Wendee Lee (English, Streamline), Meg Bauman (English, ADV)
- Full Name: Nadia La Arwall (ナディア・ラ・アルウォール Nadia Ra Aruwōru )
- Born: May 31, 1875
- Species: Atlantean (a race that came from M78 to Earth thousands of years ago)
- Origin: Tartessos, forgotten city between Europe and Africa.
The main protagonist of the series. Nadia is a 14 year old (15 toward the end of the series) who works in a circus as an acrobat in order to survive, since she is an orphan and of unknown origins. She is chased by Grandis and her associates Sanson and Hanson, who are looking for the jewel that Nadia possesses, the Blue Water. While escaping from them, she meets Jean, and from that moment the two of them will be together in the series, where she tries to discover her origins and find out the truth about her past and the Blue Water, the jewel that seems to have an enormous intrinsic power.
Nadia is quite stubborn, easily irritable, socially inept, and has the ability to talk with animals. For example, she is able to communicate easily with her pet lion cub, King. Nadia is also known among those who have knowledge of the blue water for being its possessor. She even happens to be a strict vegetarian and believes that there is no excuse for eating meat or killing (although her friends attempt to justify their reasons for doing so). Because of her unhappy past, Nadia is even extremely suspicious of all grown-ups—particularly Nemo. As such, she does not know how to act around other people, and sometimes treats them very badly. As a result of her growing love for Jean however, she comes to learn valuable lessons about friendship, respect, and trust for those around her.
In the epilogue told by a grown-up Marie in the last episode, Nadia has married Jean and they have a child. While Nadia is still a dedicated vegetarian, she is not aggressively so (as evidenced from her meals of meat and fish for Jean and their son).
- Nadia's pet white lion cub, who wears a red bandana/scarf around his neck and a ring on his tail. He is very attached to his mistress and occasionally gets jealous when Nadia gets closer to Jean. Even so, he is also very fond of Marie and often plays with her.
- Voiced by: Toshiharu Sakurai (Japanese), Carl Macek (English, Streamline), Shawn Sides (English, ADV)
King is a small lion, and he is Nadia's best friend before she meets Jean and the others. He will become eventually Marie's playmate during the episodes, playing with her all day. He is a very jealous animal, especially when Nadia and Jean become more intimate.
In the epilogue, King is still living with a now married Nadia and Jean, and has several cubs of his own.
- Jean Roque Raltique
- Jean is a young 14 year-old orphan from Paris who fell in love with Nadia at first sight. He is generous, patient, friendly, and devoted to science as well as his friends. His father is a wealthy trader who was lost at sea and declared dead, but Jean refuses to believe that and is determined to find him.
- Voiced by: Noriko Hidaka (Japanese), Ardwight Chamberlain (English, Streamline), Nathan Parsons (English, ADV)
- Full Name: Jean Rocque Raltique (ジャン・ロック・ラルティーグ Jan Rokku Rarutīgu )
- Species: Human
- Origin: Le Havre, France
- Born: March 28, 1875
The second main protagonist of the series. Jean is a young 14 year old orphan who fell in love with Nadia ever since he first laid eyes on her; unlike her, however, Jean has a completely different personality and interests. He is very generous, patient, friendly, and devoted to the things he loves, which are his friends and the love for science. He is also a genius inventor, in fact he is capable of creating complex machines at a very young age. Jean's father is a wealthy trader and ship's captain, but was recently lost at sea and is presumed dead. (We later find out that there has been a rash of mysterious disappearances of ships lately and the rumors are that a sea monster has been attacking them) Jean, however, chooses to deny them and is determined to finally find his father along with his big adventure with Nadia to find about the Blue Water. Despite being somewhat awkward when it comes to social graces around the opposite sex (such as giving compliments or lack of awareness in some cases where he's inventing and/or reading when Nadia wants his attention), Jean is genuinely well-behaved and is nice to everyone—even Gargoyle finds something to admire about his courage and cleverness.
His relationship with Nadia is one of the more central aspects of the show. When they first meet on the Eiffel Tower, Nadia refuses his overtures, but when Jean rescues her, he earns her trust. A close friendship forges between the two of them—Jean is consistently loyal to her and vows to take her to Africa someday; later their relationship begins to turn romantic, but Nadia does not know how to express her feelings to him. This leads to outbursts of anger often misdirected at Jean, yet he continually forgives her. When she is not brooding over their relationship, Nadia often goes out of her way to do something nice for him, such as cooking, encouraging him to build a gyrocopter, or comforting him when he grieves about his father (in Episode 16). Likewise, each time Nadia gets into trouble, Jean continually rescues her. Occasionally a disagreement will occur between them about certain issues (notably eating meat or the use of technology vs. nature), but they do not last long. As a result of Jean's love, Nadia is gradually transformed as a person; his optimism overcomes her pessimism, and she becomes more trusting, respectful, and caring of others.
- Marie en Carlsberg
- Marie is a 4 year-old orphan found by Nadia and Jean whose parents were murdered by the Neo-Atlanteans. The two decide to stay with her and protect her. She is incredibly intelligent and charismatic for her age. Her playmate is "King" the Lion cub.
- Voiced by: Yuko Mizutani (Japanese), Cheryl Chase (English, Streamline), Margaret Cassidy (English, ADV)
- Full Name: Marie en Carlsberg / Marie en Löwenbräu
- Species: Human
- Origin: Marseille, France
- Born: April 10, 1885
Marie is a 4 year child orphaned by the hands of Gargoyle and the Neo-Atlantean troops, who killed her parents. She is soon found by Nadia and Jean, who decide to keep her and to take good care of her. Although she is a kid, Marie is a very strong character, who is at the same time a child but also acts like an adult in difficult situations. She has a good relationship with King, her playmate. In fact, she later comes to see him as husband and wife and Nadia and Jean as her new parents. Later on, however, she will develop an interest in Sanson; in fact, in the epilogue, when a grown-up Marie tells what has happened to all the characters, she finishes her story by telling that she has married him, and is expecting their first child.
The spelling of her name is uncertain. In the episode guide she appears as "Marie", in the Japanese series books she is "Mary", Streamline Pictures calls her "Mari", and in episode 24 she signs one of her drawings as "Marry" (though this could simply be that as a four-year-old she doesn't know how to spell her name). Even so, Marie is probably the most accurate spelling, as it is the French one.
In the CD audio dramas, her full name was revealed to be "Marie en Carlsberg" (マリー・エン・カールスバーグ Marī en Kārusubāgu ), whereas in the anime's epilogue, it is "Marie en Löwenbräu" (マリー・エン・レーヴェンブロイ Marī en Rēvenburoi ).
- Grandis Granva
- Grandis is a 28 year-old woman. She was born into a rich Italian family, but is now broke and disowned by her relatives. She is the leader of the "Grandis Gang", a trio of jewel thieves. After being rescued along with Nadia, Jean and Marie by the Nautilus, she and her henchmen befriend the children. She develops a huge crush on Capt. Nemo. She also becomes a mother-figure to Nadia.
- Voiced by: Kumiko Takizawa (Japanese), Melanie MacQueen (English, Streamline), Sarah Richardson (English, ADV)
Grandis is a 28 year old who grew up in a royal Italian family. At first she was rather rich, spoiled and powerful young woman, but later when she was tricked by her first husband, who married her just for her money until he leaves her broke and alone. After her frail mistake she is exiled by her relatives and the only people who remained faithful and loyal to her were Hanson and Sanson, with whom she then formed the Grandis Gang, a group of jewel thieves. Her life and behavior change dramatically when she meets Nadia and the others; having to first steal the Blue Water, then wanting to protect them after finding out she has soft spot for them when learning about their troubles with Gargoyle. Once aboard the Nautilus she falls hopelessly in love with Captain Nemo competing and having a strict rivalry with Electra. She tries to seduce him with any power she has until the very end, but her love for him is never returned.
In the epilogue, a grown-up Marie tells us that she is alive and well, but still looking for a serious and stable love. She's quite popular though with men and is seen at the end in a golf court surrounded by them. Every man there offers her to use their club and according to Marie, "Grandis is always gallivanting around."
- Sanson is 27 years old and the muscle behind the "Grandis Gang". He considers himself an expert on handling women and is an excellent artist with a rifle. He develops a relationship with Marie and tries to help Jean grow closer to Nadia.
- Voiced by: Kenyū Horiuchi (Japanese), Tom Wyner (English, Streamline), Martin Blacker (English, ADV)
Sanson (サンソン Sanson ) is the brawn side of the team and serves as the Gratan's navigation pilot. Despite his slight yet muscular build, his strength overcomes even the most powerful of mecha. When he was younger he was slimmer and girls made fun of him; as he trained day by day he became stronger but incredibly vain. Sanson also is an outstanding marksman. He was the chauffeur to Granva's family before they lost their fortune, and he remains faithful to her until the end of the series. In the epilogue, he has married a grown-up Marie and they are expecting their first child.
His name is reminiscent of the biblical figure Samson, who appears in The Book of Judges Chapter 13 - 16., which tells the story of a man who had enormous strength, but if he were to cut his hair he would be breaking his promise with God and therefore lose all his strength. The Sanson in the series is very vain and pays particular attention to his hair.
- Hanson is 27 years old and the brains of the "Grandis Gang" who built the Gratan, the gang's small multi-purpose vehicle. Like Jean, he's into science and has a mild crush on Electra.
- Voiced by: Toshiharu Sakurai (Japanese), Steve Kramer (English, Streamline), Corey M. Gagne (English, ADV)
Hanson (ハンソン Hanson ) is the mechanic of the Grandis Gang. He has exceptional skills; he built the Gratan and lots of other devices. He is in love with Electra, but alas, his love is not returned. Jean and Hanson become close friends thanks to their mutual fascination with technology, they spend a lot of time together discussing technical details and ideas about mecha.
In the epilogue, Hanson has become an industrial giant, rich and respected-he lives in fictional world's equivalent of the Chrysler building. Having made his fortune as a manufacturer of automobiles, he still claims that he will find a girlfriend someday.
- Nemo is the captain of the Nautilus, a submarine manned by individuals looking to stop the Neo-Atlanteans at all costs. He is a mysterious man with a dark past who acts cold when he first meets Jean and Nadia, but later warms up to Jean's outgoing cheerfulness and enthusiasm. He becomes a father-figure and mentor to both Jean and (most especially) Nadia.
- Voiced by: Akio Ōtsuka (Japanese), Jeff Winkless (English, Streamline), Ev Lunning Jr. (English, ADV)
- Full Name: Eleusis La Arwall (エルシス・ラ・アルウォール Erushisu Ra Aruwōru )
- Species: Atlantean
- Origin: Tartessos, Africa
- Born: October 28, 1843
Nemo is the captain of the submarine called Nautilus, whose purpose is to destroy the Neo-Atlanteans at all costs. He is a mysterious man with a dark past; in fact only step by step we discover that he is Nadia's father and the real Emperor of Atlantis. Though he could have all mankind under his command, he chooses to live peacefully along with them on Earth, as he believes in humans and in their ability to love. While he acts cold and aloof when he first meets Jean, he nonetheless warms up to his outgoing cheerfulness and enthusiasm. Nadia, meanwhile, is very distrustful of him and is quick to accuse him of murder when he shoots a Neo-Atlantean to save her from death. However, she eventually learns to respect Nemo, and, at the end, at last acknowledges him as her father. Nemo then dies after overloading the Neo Nautilis's reactors to blow a passage out of Red Noah, permitting the rest of the cast to return to Earth.
Nemo's name is a reminiscence of the Greek city Eleusis, the place in Greece where the followers of Demeter met annually to initiate members into the ways of the Earth-goddess, and Ra, the sun-god of Heliopolis in ancient Egypt. He is based on Captain Nemo (literally meaning "no man" in Latin). He also bears a striking resemblance to another famous anime captain, Bruno J. Global/Henry J. Gloval of the SDF-1 Macross in Macross/Robotech. Additionally, he wears a uniform similar to Captain Junzo Okita from Space Battleship Yamato/Star Blazers.
- Electra is 26 years old and an orphan since the destruction of her hometown. She was saved by Captain Nemo and is his first mate on the 'Nautilus'. She and Nemo share a past experience that's never explained.
- Voiced by: Kikuko Inoue (Japanese), Edie Mirman (English, Streamline), Jennifer Stuart (English, ADV)
- Full Name: Medina La Lugensius Electra (メディナ・ラ・ルゲンシウス・エレクトラ Medina Ra Rugenshiusu Erekutora )
- Species: Human
- Born: 1865
- Origin: Tartessos, Africa
Electra is an orphan since the destruction of her hometown, after which she is saved by captain Nemo and she is the First Officer of the 'Nautilus', fighting Gargoyle and the Neo-Atlanteans. Electra is deeply in love with Nemo, although she also burgeons a deep grudge toward him for the deaths of her family. Even so, she becomes extremely envious of Grandis' mad infatuation for the Captain, igniting a heated rivalry for his love. She grows fond of Jean and his determination to learn about technology, seeing him as the equivalent of her long lost brother. Nadia, on the other hand, detests Electra and becomes increasingly (and irrationally) jealous of Jean's friendship with the First Officer (her inability to express her concern to Jean nearly ruins their own relationship); likewise, Electra fears that Nadia will somehow steal Nemo's heart away from her. Eventually, however, both open up to each other.
In the end of the series, Electra is revealed to be pregnant with Nemo's child, and Marie tells in the epilogue that she gave birth to him and raised him with love, like Nemo asked her.
- Gargoyle is the head of the Neo-Atlantean forces and is the primary antagonist. He is hell-bent on world domination, but to do that he must first destroy Nemo and the Nautilus, and take possession of the Blue Water. He is ruthless, cold and remorseless and will kill anyone who gets in his way.
- Voiced by: Motomu Kiyokawa (Japanese), Steve Bulen (English, Streamline), David Jones (English, ADV)
- Full Name: Nemesis La Algol (ネメシス・ラ・アルゴール Nemeshisu Ra Arugōru )
- Species: Human
- Born: July 21, 1843
- Origin: Tartessos, Africa
Gargoyle is the head of the Neo-Atlantean forces. He was the prime minister of Tartessos, and his main objectives are:
He considers himself an Atlantean, but he is not aware of the fact that he is one of the humans that he despises, as the mere creation of the Atlantean technology. He is a cunning yet brutal villain who speaks in a soft voice and taps into other people's weaknesses to make them comply with his wishes. His face behind the mask remains unseen until the final episode (and even then, his face is only briefly shown before he dies).
His name is also a mix of Latin and Greek mythology, as for Nemo and Electra. In first Italian dub. he's called Argo.