20,000 Leagues Under the Sea

Captain Nemo attacks ships because of his intense hatred toward a nation that imprisoned him at the penal colony island of Rura Penthe. His wife and child were killed by this nation, which also manipulated him into revealing the secrets behind his groundbreaking inventions, including the submarine technology and a powerful energy source. His attacks are acts of revenge against the world that destroyed his life.

Earlier, Nemo tells Ned that he has no use for gold or jewels, hinting at his disdain for material wealth in favor of deeper grievances.

The sea monster is actually the Nautilus, a sophisticated submarine built by Captain Nemo. The crew initially believes they are encountering a massive creature, but when the ship is rammed, it becomes clear the 'monster' is a man-made vessel. Nemo uses this disguise to roam the oceans undetected while conducting his revenge attacks.

When the explorers first discover the metallic vessel, they find it abandoned, and Aronnax sees an underwater funeral through a viewing window, hinting at the submarine's purpose.

Nemo rams and destroys the munitions ship at Rura Penthe to prevent it from delivering weapons that would cause widespread war and death. He reveals to Aronnax that his motivation is to save thousands of lives from the devastation of conflict, even though the act results in the deaths of the ship crew. This reflects his twisted moral philosophy that the few must die to save the many.

Nemo takes Aronnax to visit Rura Penthe specifically to show him the penal colony where he was imprisoned, setting up the reveal of his traumatic past.

Vulcania is Captain Nemo's secret island base where he hides his groundbreaking discoveries and the Nautilus. It serves as his sanctuary and laboratory for scientific innovation. The location is so secret that Ned discovers its coordinates only by finding hidden documents. The island becomes the site of the film's climactic destruction when Nemo, mortally wounded, sets a bomb to prevent his enemies from capturing his work.

Ned finds coordinates marking Nemo's clandestine base and attempts to send rescue messages using bottles, indicating the island's significance to the escape plan.

After the giant squid attack, Nemo's attitude shifts dramatically from vengeful warmonger to a man seeking peace. This transformation occurs because Ned Land, despite being confined in the brig for disobeying orders, escapes and heroically rescues Nemo from the squid's deadly grip. This act of courage from his prisoner causes Nemo to reconsider his path and express a desire for reconciliation with the surface world.

The squid attack forces Nemo into mortal danger, creating the opportunity for Ned to save him and shift their relationship from captor-captive to mutual respect.

Nemo is mortally wounded by a gunshot during the confrontation at Vulcania when warships surround his hideout. Despite his injuries, he plants a bomb in his hideout to destroy it rather than let it fall into enemy hands. He then navigates the Nautilus away from Vulcania, declaring he will take the submarine down for the last time. He dies as the Nautilus sinks into the depths, with his crew choosing to go down with him.

Throughout the film, Nemo demonstrates his willingness to sacrifice everything for his cause, foreshadowing his ultimate act of self-destruction.

Ned Land breaks out of the brig because he realizes they are trapped with no chance of escape while locked away. When Nemo orders the crew to their cabins and prepares to take the Nautilus down for the final time, Ned uses his harpoon to break free. He then forcibly resurfaces the submarine, crashing it onto a reef in a desperate attempt to save Aronnax and Conseil from drowning. His action, while causing the Nautilus to flood, gives them a chance at survival.

Ned's consistent desire for freedom and escape attempts throughout the movie build to this desperate final action.

Nemo allows Aronnax to stay because he respects the professor's notable research and scientific achievements. Recognizing a kindred spirit who shares his passion for discovery and knowledge, Nemo offers Aronnax the opportunity to study the ocean's secrets firsthand. Though Nemo initially returns Ned and Conseil to the deck, he ultimately allows all three to remain aboard, believing Aronnax's companions would perish without him.

When Nemo first meets Aronnax, he acknowledges the professor's work specifically, establishing their intellectual connection.

When the Nautilus becomes stranded on a reef near New Guinea, Nemo permits Ned and Conseil to go ashore to collect specimens. Ned ventures off alone seeking an escape route and discovers grim trophies of human skulls on stakes, realizing the island is inhabited by cannibals. The savage inhabitants pursue Ned and Conseil back to the shore, forcing them to flee for their lives. The Nautilus's electrical defenses ultimately protect them from the cannibals boarding the submarine.

Ned's independent nature and desire for escape lead him to ignore the stated purpose of the shore leave, putting him directly in danger.

The Nautilus is destroyed at the end of the movie. After Nemo is mortally wounded and sets a bomb at Vulcania, he commands the submarine to dive. Ned escapes the brig and forces the Nautilus to the surface, causing it to crash onto a reef and begin flooding. The submarine ultimately sinks beneath the waves as Vulcania explodes in flames. Nemo dies aboard his beloved vessel, and his crew chooses to go down with it.

Nemo's declaration that he will take the Nautilus down for the last time foreshadows the submarine's destruction.

Nemo tells Ned that he has no need for gold or jewels, explaining that a sound mind and a full belly are far more valuable than material wealth. This reflects Nemo's philosophy as a man driven by deeper pursuits, scientific discovery and revenge, rather than personal riches. His contempt for treasure contrasts sharply with Ned's fascination with wealth and escape plans centered on acquiring valuable items.

This conversation foreshadows Nemo's motivations as fundamentally ideological rather than financial, setting up his later revelations about revenge.

Nemo's final words, "There is hope for the future. And when the world is ready for a new and better life, all this will someday come to pass, in God's good time", express his belief that humanity will eventually evolve beyond war and conflict. Despite his own life of vengeance and destruction, he holds onto the hope that future generations will embrace peace and progress. These words leave Aronnax haunted but also hopeful, reflecting the film's bittersweet conclusion that redemption remains possible even after tragedy.

Nemo's shift toward peace after the squid attack sets the philosophical groundwork for these hopeful final words.