- Sina always has her daughter's back. Playful, sharp and strong-willed, Sina appreciates Moana's longing to be on the water, but also wants to protect her daughter from the fabled dangers beyond the reef.
Sina is first seen during the song, "Where You Are" as part of the loving community that makes up the tropical island of Motunui. Like her husband Tui, Sina encourages Moana to embrace her island home and follow Tui's law that prohibits anyone from sailing pass the reef. As Moana grows older, she accepts her parents' wishes, and Sina works alongside her husband in preparing Moana to one day become the next Chief of Motunui. As such, Moana takes part in solving problems throughout the village. One day, the villagers complain that the coconuts across the island are dying and that the fish are no longer in their waters. Tui and Sina see no apparent solution or cause, but Moana suggests they sail pass the reef to find fish elsewhere. This angers Tui, who confronts Moana and aggressively declares that no one is to ever leave the reef.
Moana, confused by her father's anger, laments that he simply doesn't understand her. Sina comforts her daughter and explains that her father was much like Moana at a young age. When he and his friend took a boat into the waters one night, the rough seas tipped them over. Tui managed to survive the disaster, but his best friend could not be saved in time. Sina further explains that Tui's aggression is out of love for his family and people.
Quite some time afterward, Sina and Tui gather the villagers to discuss their island's increasing crises. Moana arrives and claims that their ancestors were great voyagers, meaning they should venture into the sea and return the legendary heart of Te Fiti (as its removal is the cause of their island's plaguing curse) to save their home. This leads to another confrontation between Moana and Tui, but they are both horrified to receive word of Gramma Tala's failing health. Sina can hardly hold back tears as she watches her mother-in-law die before her, and as a final promise to her grandmother, Moana leaves the hut to pack her resources in preparation for her mission to return Te Fiti's heart. Though Sina is mortified to see her daughter leave, she supports her decision and helps pack, bidding farewell as Moana disappears into the night.
Sina briefly appears later on during Moana's nightmare, where she watches her parents die as the curse consumes the entirety of the island.
Sina is last seen after Moana returns home from her successful mission. Sina warmly embraces her daughter and the family is reunited once more. Due to Moana's bravery, the villagers are free to voyage the open oceans once more, which Sina joins in.
- Sina is the sixth mother of a Disney Princess to be alive; preceded by Queen Leah (Aurora's mother), Fa Li (Mulan's mother), Eudora (Tiana's mother), Queen Arianna (Rapunzel's mother), and Queen Elinor (Merida's mother).
- The name Sina means "treasure; God is gracious."
- "New ‘Moana’ Photos and Character Details Introduce You to the Animated Cast". Screencrush (July 25, 2016).