米蘭達·麥錢特不情願地前往塞爾基島海岸與她的母親生活在一起，在那裡她很快就聽說了海底漫步者。根據當地的傳說，牠們是一種半人海怪的生物。
Miranda Merchant reluctantly arrives on the shores of Selkie Island to live with her mother where she soon learns about the Seawalkers, who, according to local legend, are half human and half sea creature.
