Hae-jin, 29, struggles to adapt to life in Seoul and returns to her hometown of Jeju. There, she reunites with her mother, Ok-ran, and her grandmother, Kang-ja, who has spent her life as a haenyeo. Hae-jin decides to become a haenyeo, but Ok-ran strongly opposes it. The conflict between them intensifies, while Kang-ja is diagnosed with dementia.