The Sapphire Mystery, but it's supposed to be a little white lion, aka Nadia of the Incredible Sea. It is said to be based on Jules Verne's novel Twenty Thousand Leagues Under the Sea , but in itself it doesn't have much to do with the original

English translation 1: "Nadia: The Secret of Blue Water"

Twenty Thousand Leagues Under the Sea (The Mystery of the Sapphire) English translation 2: "Nadia of the Mysterious Seas"

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Introduced in China around 1992, Shanghai was broadcast by the Education Channel and currently people around 20 years old mostly watch the Chinese dubbed version in elementary school. I think it's a good idea to look back at it (values have changed, and rewatching it will give you a completely different feeling, just like you would if you watched EVA in elementary school, and now you're watching it again ^^), and if you haven't watched it, it's a good idea to put it at the top of your anime-watching agenda.

It should be this