[[quoteright:250:http://static.tvtropes.org/pmwiki/pub/images/blue6_2597.jpg]]

->''"A world of endless blue..."''

A four-episode {{anime}}, taking place after the apocalypic flooding of Earth by EmperorScientist Dr. Zorndyke. With the remaining cities ravaged by Zorndyke's army of [[HalfHumanHybrid fish-human hybrids]] - his "children" and intended heirs to the new world - the last hopes of humanity fall on the remaining submarine fleet, the titular No.6, and [[BrilliantButLazy cadet-turned-slacker]] Tetsu Hayami.

Aired on Creator/{{Toonami}} back in its glory days. After Creator/BandaiEntertainment completely ceased DVD production, the rights are now in the hands of Creator/DiscotekMedia, who have so far rereleased the series on DVD and Blu-Ray.

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!!Tropes:

* ADogNamedDog[=/=]AKindOfOne: In the Japanese version, Mutio's species is referred to as...Mutio.
* AfterTheEnd: All coastal human cities are underwater as a result of Zorndyke's arctic melting.
* AllTheOtherReindeer: Mutio isn't exactly popular among her kind for being a pacifist that interacts with a human. Being the only one of her sisters with red instead of blue eyes makes her stand out even more.
* AmazonBrigade: Mutio and her sisters, who are elite pilots for the Umigumos in Zorndyke's navy.
* AntiHero: Kino.
* AntiVillain: Zorndyke, depending on whether you sympathize with his motivations.
* ApocalypseHow: A Class 1. Zorndyke flooded earth's coastal areas. [[spoiler:And he is planning to turn it into a Class 4]].
* BecauseYouWereNiceToMe: When Hayami is separated from the Blue Fleet and left drifting in the Pacific, he is saved from drowning by Mutio. Why? Because he saved her in Tokyo Bay, only two days earlier.
* BigSisterInstinct: Kino is hinted to have this towards Huang.
* BittersweetEnding
* TheCallKnowsWhereYouLive: Zorndyke's navy attacks Tokyo shortly after Hayami turns down Kino's offer to join Blue Fleet.
* CatGirl: A few of these, including a lynx-woman aboard the Phantom Ship, and Zorndyke's "daughter" that recites poetry. Mutio and her sisters also have elements of this trope, in addition to being FishPeople.
* CensorDecoy: When the show ran on Toonami, the censors objected to the line "Go to hell!" by Iga in the final episode. It was replaced by ''"Suck on this!"'', which has ''much'' worse implications.
* ChildProdigy: Huang Mei-Ling is ten years old and operates complex sonar machinery for a military vessel.
* CluelessAesop: Something about a cycle of revenge when the enemy really is AlwaysChaoticEvil (good or at least nice members are killed), are killing the remains of humanity, and is enjoying it greatly.
* ConspicuousCG: Gonzo were never known for their ability to believably incorporate CG into their animated series. ''Blue Sub 6'' is among their earliest efforts, so one might forgive them in this case - particularly as the rest of the animation is gorgeous.
* CoolShip: Blue Sub No. 6, and many others.
* CuteMonsterGirl: Mutio and the other fish-girls, as well as the furry girl at the end.
* CuteMute: Mutio, just about. The only word she can say is Hayami.
* DarthVaderClone: Verg.
* DefeatMeansFriendship: After Hayami cripples and maroons her Umigumo, Hayami saves Mutio, and she becomes smitten with him later on.
* DrivenToSuicide: Dr. Zorndyke's old colleague blew himself up rather than joined him.
* EmperorScientist: Dr. Zorndyke is the poster boy for this trope.
* TheEndOfTheWorldAsWeKnowIt: What sets of the main plot of the series, is Zorndyke plan to reverse the magnetic poles of the earth, thus rendering it completely uninhabitable.
* EvilRedhead: Verg, who has a series of red, curly dreadlock-like hairs on his head.
* EvilSoundsDeep: Averted with Verg, who (due to his speech synthesizer) has a screechy high-pitched voice that resembles a mixture of [[Franchise/{{Transformers}} Starscream]] and the sea otters from ''WesternAnimation/SouthPark''. Played straight once he removes it, and starts speaking in booming, animalistic growls.
* {{Expy}}: Zorndyke is Dr. Moreau, with shades of [[Film/ApocalypseNow Colonel Kurtz]] and [[Film/TheSpyWhoLovedMe Karl Stromberg]].
* FanService: Hayami's [[ShirtlessScene shirtless scene]] at his introduction and in the third episode, plus Kino's skin-tight body suit, which she often unzips halfway for some cleavage. Mutio speaks for herself...
* FishPeople: Verg, Mutio, her sisters, and most of Zorndyke's navy.
* FragileFlower: Huang, in spades.
* FriendOrIdolDecision: Implied in the opening of episode 3. Mutio is carrying the dying body of one of her sisters when she sees Hayami's safety capsule floating in the water. Since we don't see the sister's body when she rescues Hayami, it appears she abandoned her sister just to save him.
* GettingCrapPastTheRadar: The TV-Y7 version that ran on Toonami left in Mutio's nudity, albeit with the nipples removed (making it BarbieDollAnatomy) - still, this is shocking considering ''Anime/TenchiMuyo'' had to get bathing suits digitally painted on its nude female characters.
** Iga's "Get that damn gate open now!" was left intact in the second episode of the TV-Y7 version.
* AGodAmI: Subverted. Zorndyke doesn't think of himself as one because he thinks he is "not nearly so arrogant as that".
* HeroicSacrifice: The Japanese SSGN that attacks the Ghost Ship.
* HiddenElfVillage: [[spoiler:There is a village of hybrids hidden behind the mist where the North Pole formerly stood.]]
* HighHeelFaceTurn: Mutio.
* [[HotSubOnSubAction Hot Sub on Whale Action]]: Most of the fight scenes.
* HopelessWar
* {{Hypocrite}}: Zorndyke believes HumansAreTheRealMonsters and would screw everything up. He was the bastard that screwed everything up and refuses to own up and instead continues on like some NietzscheWannabe.
* InterSpeciesRomance: Hayami and Mutio. {{Enforced}} or at least friendship for humanity and Zorndyke's creations even though most of Zorndyke's creations are evil/do nothing in the war.
* KarmaHoudini: Verg. Despite killing many innocent people in Tokyo, destroying Blue Dome, allowing Red Spot to be torpedoed by Blue 6, and beating both Mutio and Hayami to a bloody pulp, he still manages to get away in the end, with nothing more than a few scars and bruises for his troubles. Even Mutio shows up to forgive him and bring him to the other hybrids to mourn Zorndyke's loss.
* LecherousLicking: Verg does this to Mutio and one of her sisters in episode 2, during his VillainousBreakdown.
* LiteralChangeOfHeart: Turns out that [[spoiler: Dr. Zorndyke removed his own heart and used it to power the Earth's destabilizing magnetic field]].
* [[MacrossMissileMassacre Macross Torpedo Massacre]]
* MadScientist: How the world (and a fair number of viewers) view Zorndyke.
* MermaidProblem: Averted. ''Implicitly.''
* MickeyMousing: HotSubOnSubAction choreographed to bossanova. It's as awesome as it sounds.
* MisanthropeSupreme: Why Zorndyke created his fish-people and flooded the world in the first place.
** [[KillAllHumans Zorndyke himself is probably by far the worst]].
* NiceJobBreakingItHero: [[spoiler:See below. No. 6, unintentionally, leads Verg and the Ghost Ship right to the secret base of Blue Fleet]].
* MsFanservice: Kino and Mutio.
* NoHoldsBarredBeatdown: Verg to Hayami at the end.
** Not to mention the severe (though short) beatdown Mutio receives at the beginning of episode 4 (and just before the start of the episode) with a sheathed, heavy sword. Leaving her just enough strength to limp-swim away, bloody and injured.
* NotWorthKilling: Verg was beating Hayami to near-death, until he sees Kino crying with Hayami in her arms. He then no longer has any desires to kill any more humans.
* NukeEm: Humanity's back up plan to finish Zorndyke.
** "So that's the plan? Nuke the psycho? ''That's'' original." -Hayami
* OceanPunk
* OurMermaidsAreDifferent: Mutio and her sisters.
* PerfectPacifistPeople: Shows up towards the end. RuleOfSymbolism makes the place where they live seem like Heaven. Did we mention they've found by the protagonist at the end of a war?
* PirateParrot: Verg has one during a few scenes. It is [[WhatHappenedToTheMouse unknown what happens to it later on]].
* PsychopathicManchild: Verg. He wants to please Zorndyke, whom he calls "Papa", but is extremely violent and prone to throwing temper tantrums.
* [[RecycledInSpace Recycled UNDER WATER!]]: The series is essentially a retelling of ''Literature/TheIslandOfDoctorMoreau'' WITH FISH PEOPLE.
* RedEyesTakeWarning: ''Averted''. Mutio has red eyes that more then once glow in the dark underwater scenes, yet she is kind and quite harmless. Her blue-eyed sisters on the other hand...
* SayMyName: "Ha...ya...mi!"
* ScaryShinyGlasses: Zorndyke
* ScavengerWorld: As a result of many of the former cities being underwater now.
* SciFiWritersHaveNoSenseOfScale: While 1 billion people seems like a lot, given the effects of the flood (enough to half-way sink a skyscraper) it should've killed a lot more. To get an idea: there are about 7 billion people currently in the world.
** However the flooding due to polar ice melt would not have occurred instantaneously and it is likely that mass evacuation inland occurred. Indeed the vast bulk of the deaths are most likely due to subsequent starvation and disease as the inland areas would have been ill-equipped to support such a massive refugee population, and to attacks by Zorndyke's forces. Musuca 17 / Red Spot for instance relates that his species were tasked to "wander the seven seas, destroying human cities".
** The English dub over-corrects and claims 10 billion people died. Though they ''did'' mention that humanity basically solved World Hunger some time before the war started, so that could explain a population boom.
* SelfFulfillingProphecy: Zorndyke believed HumansAreTheRealMonsters and would ruin everything. Naturally he ruined everything.
* SexyPackaging: The blu-ray cover shows Kino in an [[https://www.nipponart.de/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/b/l/blue_sub_bd_2d_fsk.jpg overly sexy outfit]] which she never wears in the anime.
* ShutUpHannibal: Mutio lashes out at Verg when he yells at her. [[OhCrap It didn't help her situation.]]
* SilenceYouFool: Verg in the dub.
* SoundtrackDissonance: It's debatable whether the rather discordant, wailing jazz soundtrack fits the tone of the series.
* StarCrossedLovers: Though at least it's implied by the final episode credits that Hayami and Mutio will eventually get back together once things finally settle down.
* SunkenCity: Tokyo. One early episode even features HotSubOnSubAction within the cramped man-made canyons of the submerged skyscrapers.
* TokyoIsTheCenterOfTheUniverse: Tokyo is where the series starts, and where we first meet the protagonists ''and'' most of the antagonists.
* TransformingMecha: The Grampus mini-sub.
* {{Tsundere}}: Hayami. Mostly tsun.
* UnderwaterBase: The headquarters of the Blue fleet. [[spoiler:It is destroyed minutes after it is introduced, by Verg, who followed No. 6]].
* UnderwaterRuins: See above. We see mostly Tokyo, but is implied that most of the world is flooded.
* VillainousBreakdown: Verg in episodes 2 and 4.
* VillainousBSOD: Mutio in episode 2. After being saved by Hayami and finding out that one of her sisters had been killed during the battle, she becomes catatonic for the remainder of the episode. She doesn't even try to run away like the rest of her sisters during Verg's VillainousBreakdown.
* WalkingShirtlessScene: Hayami, at several points in the anime. Also, Verg in the last episode.
* WellDoneSonGuy: Verg.
* WellIntentionedExtremist: Zorndyke.
* WhyDontYouJustShootHim: Verg's definition of "banishing" Mutio appears to be "having twenty of her sisters guard her and hold her in place, even when there's a battle raging outside", when it would have been ''significantly'' easier to either kill her or ''really'' banish her from the ship.
* XMeetsY: ''Film/{{Waterworld}}'' meets ''Literature/TheIslandOfDoctorMoreau'', ''Film/ApocalypseNow'', and various submarine movies.
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