An air/sea/land battleship captain (Tadao Takashima) rescues his daughter (Yoko Fujiyama) from the earthquaking undersea dwellers of Mu.
Atragon, released in Japan as Kaitei Gunkan (海底軍艦?, lit. "Undersea Warship"), is a 1963 Toho tokusatsu film based on a series of juvenile adventure novels under the banner Kaitei Gunkan by Shunrō Oshikawa (heavily influenced by Jules Verne) and the illustrated story Kaitei Okoku ("The Undersea Kingdom") by illustrator Shigeru Komatsuzaki, serialized in a monthly magazine for boys. Komatsuzaki also served as an uncredited visual designer, as he had on The Mysterians (1957) and Battle in Outer Space (1959). visualizing the titular super weapon, among others.
The film was one of several tokusatsu collaborations of director Ishirō Honda, screenwriter Shinichi Sekizawa, and special effects director Eiji Tsuburaya. It features Jun Tazaki, an authority figure regular to tokusatsu, in his largest genre role as the conflicted Captain Jinguji of the super-submarine "轟天号" Gotengo or Roaring Heavens — the suffix, "号" (go), simply denotes the object as a ship. The supersub was dubbed Atragon in the English-language U.S. version, released in 1965 by American International Pictures.
As was the case in several other 1960s tokusatsu eiga (visual effects films), producer Tomoyuki Tanaka insisted that a daikaiju be incorporated into the storyline for marketing purposes, to which Tsuburaya designed Manda—a Chinese dragon-like sea serpent that would subsequently appear in several films in the Godzilla series. The Atragon itself, slightly modified, would reappear in several other movies, including Godzilla: Final Wars and Super Star Fleet Sazer X The Movie: Fight! Star Warriors.