A small pounamu stone that is the mystical heart of the island goddess, Te Fiti, is stolen by the wind and sea demigod, Maui, who plans to give it to humanity as a gift. As Maui makes his escape, he is attacked by Te Kā, a lava demon of Earth and fire, causing his power-granting magical fishhook and the heart of Te Fiti to be lost in the ocean.
A millennium later, Moana, daughter and heir of the chief on the small Polynesian island of Motunui, is chosen by the ocean to receive the heart, but drops it when her father, Tui, comes to get her. He insists the island provides everything the villagers need. Years later, a blight strikes the island as fish become scarce and the island’s vegetation begins dying. Moana proposes going beyond the reef to find more fish. Tui rejects her request, claiming that sailing past the reef is forbidden.
Moana’s grandmother, Tala, shows Moana a secret cave behind a waterfall where she finds boats inside and discovers her ancestors were voyagers, sailing and discovering new islands across the world. Tala explains that they stopped voyaging because Maui stole the heart of Te Fiti, causing monsters to appear in the ocean. Tala then says Te Kā’s darkness has been spreading from island to island, slowly killing them. Tala returns the heart of Te Fiti to Moana, which she had recovered after Moana dropped it.
Tala falls ill, and with her dying breaths, tells Moana to set sail. Moana and her pet rooster, Heihei, depart in a drua to find Maui. A manta ray, Tala’s reincarnation, follows. After a typhoon wave flips her sailboat and knocks her unconscious, she awakens the next morning on an island inhabited by Maui, who traps her in a cave and takes her sailboat to search for his fishhook. After escaping and catching up to Maui, Moana tries to convince him to return the heart, but Maui refuses, fearing its power will attract dark creatures.