Chapter 1: A Shifting Reef

The novel opens with an introduction to the main character, Professor Pierre Aronnax, a French marine biologist. He is invited to join an expedition aboard the USS Abraham Lincoln to hunt down and destroy a mysterious sea monster that has been plaguing ships. After being thrown overboard during a sighting of the monster, Professor Aronnax and his companions, Conseil and Ned Land, discover the creature is actually a submarine, the Nautilus, belonging to the enigmatic Captain Nemo.

Chapter 5: The Coral Kingdom

The Nautilus travels to a coral reef, where Professor Aronnax and Conseil explore the underwater world. They encounter a variety of sea creatures, including a giant squid, a school of electric eels, and an undersea forest of kelp. Captain Nemo also shows them a pearl diving operation and a sunken ship that has become a habitat for fish and other marine life.

Chapter 10: The Underwater Coal Mines

The Nautilus dives deep beneath the ocean to explore underwater coal mines. Captain Nemo explains that he has been ostracized from society and has built the Nautilus as a means to escape and explore the world without interference. He shows Professor Aronnax the advanced technology that powers the submarine, including an air purification system and a powerful electric battery.

Chapter 15: A Fight with a Squid

The Nautilus is attacked by a giant squid, and the crew must fight to protect the ship. The fight is long and intense, and the squid manages to wrap its tentacles around the Nautilus. However, Captain Nemo is able to break free and the crew successfully kills the squid. Professor Aronnax is both awe-struck and disturbed by the experience, and begins to wonder about the darkness that may lie within Captain Nemo.

Chapter 20: The Torres Strait

The Nautilus navigates through the treacherous Torres Strait, a narrow body of water between Australia and New Guinea. They see a wrecked ship and a group of natives who attempt to attack the submarine. Captain Nemo orders the Nautilus to dive deeper and avoid confrontation. Professor Aronnax reflects on the implications of being an outsider in an unknown world, and the potential danger that can arise from such a position.

Chapter 23: The South Pole

The Nautilus reaches the South Pole, and the crew sees the breathtaking scenery of the frozen wasteland. However, tensions begin to rise as Professor Aronnax and his crewmates contemplate the possibility of never returning to their home countries. Captain Nemo is secretive and mysterious, and there is a sense of isolation and sadness aboard the Nautilus. The novel's themes of exploration, discovery, and the limits of human knowledge are emphasized in this chapter.

Chapter 27: The Red Sea

The Nautilus travels through the Red Sea, where they encounter a school of sperm whales and are attacked by a group of rays. Professor Aronnax and Ned Land attempt to escape the submarine but are thwarted by Captain Nemo. The tension between the crewmembers and Captain Nemo reaches a breaking point, and they are forced to come to terms with their limited options and uncertain future. The chapter ends with the Nautilus heading towards an unknown destination, leaving the reader wondering about the fate of the crew.