While the presence of a large quantity of water enclosed or infiltrated in solid rocks was considered probable, it was not yet precisely known how deep it might be. However, in 2016, an ocean of water was found 620 miles below Earth's surface; in a first study, researchers from Florida State University and the University of Edinburgh estimated that water existed far deeper in the Earth than previously thought; stored in a mineral called brucite. Although the exact amount of water is unknown, researchers believe it could account for as much as 1.5 percent of the weight of the planet —the same amount of water as all the world's oceans put together. I don't know if this body of water has yet been given a name; but may I suggest Lidenbrock Sea. But enough about science; this is a fantastic and really! fun adventure. To analyze its scientific accuracy is to totally obfuscate the issue, and spoil the fun of reading it. Enjoy!
Journey to the center of the Earth is a novel of adventures, written in 1864 by Jules Verne, re-published in large octavo on May 13, 1867. The novel deals with the discovery of an ancient runic manuscript by a German scholar who, with his nephew and a guide, undertakes a journey to the center of the earth by entering through an extinct Icelandic volcano, the Snæfellsjökull.