Gainax, the production company, has a reputation for being frugal when it comes to animation in some of their productions. This sometimes means that they will reuse animation; not only from the current production, but from other series they've produced if the budget becomes too tight. This is apparent in one episode of this series - when the Nautilus is doing battle against a pack of Garfish, footage of missile tubes opening is lifted from Gunbuster (1988). Also, stock footage of the ocean waves beating against the sand from the Island episodes and the explosion caused by the Tower of Babel's energy beam in this series ends up being used again in Neon Genesis Evangelion (1995).
This was originally intended to be a 30-part TV series, but because the show was so successful in Japan, backing distributor NHK Enterprises requested GAINAX to produce more episodes, extending the episode count to 39.
Shortly after the series ended, NHK Enterprises opted to produce a theatrical movie of Nadia: The Secret of Blue Water (1990), which was done without the participation of the original creative team who worked on the series. Approximately one third of the 90-minute feature consists of recycled clips from the show.
Development began in the 1970s with Hayao Miyazaki selected by Toho Company to develop a television series. The project didn't go through until 1988 when Toho appointed Gainax to produce the series based on Miyazaki's original outline.
At the completion of the series, Gainax had lost ¥80 million on the project and had no rights to the series itself. However, they were allowed rights to produce a video game of the series, which would set record earnings for the company.