Mi-ja and Young-sook, two girls living on the Korean island of Jeju, are best friends who come from very different backgrounds. When they are old enough, they begin working in the sea with their village’s all-female diving collective, led by Young-sook’s mother. As the girls take up their positions as baby divers, they know they are beginning a life of excitement and responsibility but also danger. Little do they know that after surviving hundreds of dives and developing the closest of bonds, forces outside their control will push their friendship to the breaking point.