The film sets in 1985. Atlanna (Nicole Kidman), Queen of Atlantis, flees an arranged marriage and ends up in Amnesty Bay, Massachusetts. There she is found by a lonely lighthouse keeper (Temuera Morrison), the two fall in love and have little Arthur. While his mother is soon forced to leave the family, the boy discovers his special abilities. Among other things, he can breathe and speak underwater and communicate with the living beings there. Atlantis is now ruled by Arthur’s half-brother Orm (Patrick Wilson). His advisor Vulko (Willem Dafoe) secretly takes care of Arthur, who, however, does not want to know anything about his mother’s home.
Unsurprisingly, Arthur alias Aquaman then becomes the last hope on earth as the story progresses. Orm not only plans to forcibly unite the different kingdoms underwater, but also wants to take revenge on the people of the surface for the pollution of the oceans and subjugate them. Princess Mera (Amber Heard), daughter of King Nereus (Dolph Lundgren), convinces Arthur to fight his brother. The two go in search of a legendary trident. On their heels is a pirate (Yahya Abdul-Mateen II), equipped by Orm with dangerous weapons technology.