Three years after her adventure with the demigod Maui and the island goddess Te Fiti,[c] Moana spends her days exploring other islands near her home island of Motunui in the hope of finding people connected to the ocean.

In a vision, her ancestor, Tautai Vasa, reveals why none of those people are connected anymore: the malicious storm god Nalo wanted power over the mortals, so he sunk a legendary island called Motufetu—which connected all islands—down to the depths of the ocean. Tautai further warns that the people of Motunui will go extinct in the future if Moana cannot find a way to raise Motufetu. She assembles a crew of people from Motunui—clever craftswoman Loto, historian and Maui fanboy Moni, and grumpy elderly farmer Keke, alongside her pet pig and rooster, Pua and Heihei—to follow the path of a comet across the ocean towards Motufetu.