Off Jeju Province, on the islet of Udo, women called haenyeo have dived without air tanks for over a thousand years, descending 10 to 20 meters to harvest seaweed and shellfish, working seven to eight hours a day without a sip of fresh water. Filmed over seven years, the documentary follows a three-generation diving family, a woman who took up diving to pay off her husband's gambling debts, and an older diver who keeps returning to the sea despite losing her own daughter, also a haenyeo, to it. It explains the community's internal ranking system, Groups A, B, and C, sorted by lung capacity and breath length believed to be fixed at birth, and the ever-present danger of mulsum, the fatal moment when a diver runs out of air and swallows water while pushing past her limit. Interviews with the women themselves, underwater footage of their dives, and the eerie whistling sumbisori they exhale on surfacing carry the film's account of a vanishing way of life built entirely around controlling desire and holding one's breath.