So we did cross the underground sea! But the magnetic storm made our compass point the wrong way!
And so our journey ends. We made it! Arne Saknussemm was right! We made the "Journey to the interior of the Earth"! But we called it the "center" due to a translation error. We were never more than a few miles down, which is why the pressure didn't kill us, and why the caves didn't collapse.
That proves it! Grauben was right! The Martians could have come from inside the Earth! That settles it! We have to go back, and this time, reach the center of the Earth!
Next: The Goddess of Atvatabar