"A sea of endless blue..."

A four-episode anime, taking place after the apocalypic flooding of Earth by Emperor Scientist Dr. Zorndyke. With the remaining cities ravaged by Zorndyke's army of 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 aquaphobic cadet-turned-slacker Tetsu Hayami.

Aired on Toonami back in its glory days.

• A God Am I: Subverted. Zorndyke doesn't think of himself as one because he thinks he is "not nearly so arrogant as that".
• After the End: All coastal human cities are underwater as a result of Zorndyke's arctic melting.
• Anti-Hero: Kino.
• Anti-Villain: Zorndyke, depending on whether you sympathize with his motivations.
• Apocalypse How: A Class 1. Zorndyke flooded earth's coastal areas. And he is planning to turn it into a Class 4.
• Bittersweet Ending
• Child Prodigy: Mei-Ling is ten years old and operates complex sonar machinery for a military vessel.
• Conspicuous CG: 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.
• Cool Ship: Blue Sub No. 6, and many others.
• Cute Monster Girl: Mutio and the other fish-girls, as well as the furry girl at the end.
• Cute Mute: Mutio, just about. The only word she can say is Hayami.
• Emperor Scientist: Dr. Zorndyke is the poster boy for this trope.
• Expy: Zorndyke is Dr. Moreau, more or less. See below.
• Fan Service: Hayami's 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.
• Fish People
• Heroic Sacrifice: The Japanese SSGN that attacks the Ghost Ship.
• Hot Sub On Whale Action: Most of the fight scenes.
• Hopeless War
• Humans Are the Real Monsters: Why Zorndyke created his fish-people and flooded the world in the first place.
  • Zorndyke himself is probably by far the worst.
• Interspecies Romance: Hayami and Mutio.
• Literal Change of Heart: Turns out that Dr. Zorndyke removed his own heart and used it to power the Earth's destabilizing magnetic field.
• Macross Torpedo Massacre
• Mad Scientist: How the world (and a fair number of viewers) view Zorndyke.
• Mermaid Problem: Averted. Implicitly.
• Mickey Mousing: Hot Sub-On-Sub Action choreographed to bossanova. It's as awesome as it sounds.
• Nice Job Breaking It, Hero: See below. No. 6, unintentionally, leads Verg and the Ghost Ship right to the secret base of Blue Fleet.
• No Export for You: The very obscure prequel and sequel video games.
  • To a lesser extent, a R2 UK release, or, to better put it, the lack of such.
• No-Holds-Barred Beatdown: 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.
• Nuke'Em: Humanity's back up plan to finish Zorndyke.
  • "So that's the plan? Nuke the psycho? THAT'S original" -Hayami
• Ocean Punk
• Our Mermaids Are Different: Mutio and her sisters.
• Psychopathic Manchild: Verg. He wants to please Zorndyke, whom he calls "Papa", but is extremely violent and prone to throwing temper tantrums.
• Recycled UNDER WATER!: The series is essentially a retelling of The Island of Dr. Moreau WITH FISH PEOPLE.
• Scary Shiny Glasses: Zorndyke
• Scavenger World: As a result of many of the former cities being underwater know.
• Sci-Fi Writers Have No Sense of Scale: 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.
  • The english dub over-corrects and claims 10 billion people died.
• Silence, You Fool: Verg in the dub.
• Soundtrack Dissonance: It's debatable whether the rather discordant, wailing jazz soundtrack fits the tone of the series.
• Star-Crossed Lovers: 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.
• The End of the World as We Know It: 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.
• Transforming Mecha: The Grampus mini-sub.
• Tsundere: Hayami. Mostly tsun.
• Underwater Base: The headquarters of the Blue fleet. It is destroyed minutes after it is introduced, by Verg, who followed No. 6.
• Underwater Ruins: See above. We see mostly Tokyo, but is implied that most of the world is flooded.
• "Well Done, Son" Guy: Verg.
• Well-Intentioned Extremist: Zorndyke.