Watch FilmoFlix. In Celtic and Norse mythology, selkies, meaning ‘seal-folk’, are beings capable of therianthropy: changing from seal to human form. Emerging when the time and tides are correct, seducing or being held captive by human lovers, the composite shape shifting water siren emerges from her underwater world to ours, casting her spell of seductive and violent dance. Is it love and desire or appetite and malice?