This is a mythic land where no outsider has ever set foot. The spirit-like dwellers there, however, know us mortals well. They are responsible for human emotions and desires, for seasons, weather, the elapsing of time... 
 
Our protagonist, a spirit girl named Chun, has just turned sixteen and goes in the form of a dolphin to explore the earthly part of the sea, to see what the human world is like. While cruising at sea, Chun gets caught in a storm and finds herself enmeshed in a fishing net. A human boy spots her and comes to her rescue, trying to free Chun from the entanglement. By accident, the boy drowns leaving Chun wretched and heartbroken. 
 
Da Hai tells an absorbing and bittersweet story of sacrifice and redemption when Chun is determined to bring back to life the boy's soul, now in the form of a little white fish. Da Hai is about an adolescent coming to terms with her limitations, and a spirit, coming into possession of her powers [...] dealing with the difficult issues of death, love and maturing emotions with empathy and nuance. 
 
(Source: The feature film brochure)