Den 12. august 2000 rammer katastrofen den russiske atomubåd Kursk. En torpedo eksploderer, hvorpå ubåden går til bunds med mand og mus. Mens besætningen kæmper for deres liv, kaster deres familier sig ud i en desperat kamp mod de russiske myndigheder, der nægter at tage imod international hjælp for at redde de overlevende.

En erhvervsdykker sidder fast på havbunden med forsvindende lidt ilt og intet håb om at blive reddet i tide. Så han forsøger at redde sig selv.

Survivors of a sinking ship are rescued by Captain Nemo and his submarine crew. They are taken to an underwater city where they may spend the rest of their lives.

On a volcanic island near the Kingdom of Hetvia rules Count Dakkar, a benevolent leader and scientist who has eliminated class distinction among the island's inhabitants. Dakkar, his sister Sonia and her fiance, engineer Nicolai Roget have designed a submarine which Roget pilots on its initial voyage just before the island is overrun by Baron Falon, despotic ruler of Hetvia. Falon sets out after Roget in a second submarine and the two craft, diving to the ocean's floor, discover a strange land populated by dragons, giant squid and an eerie undiscovered humanoid race.