How many meters under the sea is 20000 leagues?

Answer 1

A league was about 3 miles in length

As we talking about the sea, we'd better use the nautical mile (slightly longer than the statute (land) mile), meaning 1 league is 3 x 1852m ~= 5.6km,

So 20,000 leagues would be 111,120,000m (111,120km).

The diameter of the earth is approx 12,750km, so 20,000 leagues under the sea would be all the way through the earth and nearly 100,000km beyond it into space, a little over a quarter of the way to the moon (about 385,000km away) - if it referred to the depth.

(The furthest depth mention in the book is 4 leagues or about 13824m; the 20,000 leagues is the distance travelled along under the sea as opposed to along on the sea)