Tabor island (AKA Maria-Theresa reef) where Ayrton was marooned, and which was long believed to sit at the stated location, was later proven to not exist at all. What's interesting is that the Ernest Legouve reef, a similar phantom island close to the purported Tabor's position, sits roughly in the same location as Verne's Lincoln island.
According to Cyrus, the Pacific Ocean will one day be replaced by a vast coral reef the size of a continent.
Tear Jerker: Poor Jup. Nemo's back story is probably also a qualifier.
Values Dissonance: While Fair for Its Day, it's still a bit of a shock when the narration cheerfully informs that Pencroff and Nab are naturally on kitchen duty since one's a sailor and the other a negro.