The Mystery of the Lost Continent
The victims of Gargoyle's latest attack are taken to the long-forgotten underworld of Atlantis to be buried. While there, Jean discovers that his father's ship was sunk by the Garfish. Nadia also learns that she must keep the Blue Water at all costs, no matter what pain or damage it may cause.
Aired 24/08/1990EP 16 - The Mystery of the Lost Continent

Nadia: The Secret of Blue Water
In 1889, the world is on the pinnacle of great discoveries in technology. In mankind's grasp for the future, a sinister foe known only as Gargoyle, obsessed with restoring the former Atlantean empire to the glory it once held, begins his plans to take over the world. Nadia, with the help of a young inventor, Jean Raltique, and the mysterious captain Nemo of the submarine Nautilus, must fight to save the world from Gargoyle and Neo-Atlantis. Based on the Novel '20,000 Leagues Under the Sea' by Jules Verne.
(Source: Anime News Network)