The Nautilus continues heading south, out into the middle of the Atlantic. There's no chance for escape anytime soon.
They pass through the area known as the Sargasso Sea, a place where seaweed as thick as a carpet covers the ocean.
For over two weeks, the Nautilus keeps the same course. They stay in the middle of the Atlantic, far away from the coast.
Aronnax gets a little uneasy. He considers asking Nemo to let them go, but—big surprise—he doesn't do anything.
Nothing much happens during these two weeks. They see a couple of ships and not much else.
Oh, and Aronnax and Conseil look at some fish. Yeah, so nothing really happens.
By March 13, Aronnax notes that they've covered 13,000 leagues. Nemo decides to take the Nautilus diving.
He gets the ship down 16,000 meters (or four leagues) under the ocean. He even takes a picture for Aronnax, to keep as a little souvenir. (To put this voyage into perspective, the deepest part of the ocean—at least that we know about—is the Pacific's Mariana Trench. It's thought to be around 11,000 meters deep at its deepest point. And, yeah, a submarine really can't handle the pressure down there.)
Nemo doesn't want to hang out down there too long. He knows the Nautilus can't take too much deep-sea diving. Thankfully, four minutes, later they're back at the surface. (Even modern subs can't resurface that quickly; Verne overshot a little on this one.)