From Zelda Legends Wiki
Marin is the Link's Awakening equivalent of Zelda... or at least, she's what Link's imagination creates to represent Zelda. A kind, gifted girl, she plays a very vital role in the LA story.
The only character other than Link to appear in the opening scene (if you don't count the egg), she is responsible for finding Link after the storm and nursing him back to health. Link awakens for the first time in her and her father Talon's house.
Marin and Link's love story is one of the most subtle to grace the video game industry, but is nonetheless touching. They never have a chance to actually do anything with their mutual affection (they do get their picture taken when standing above a cliff), but the connection definately exists.
Link learns a song from her early on in the story, has her follow him all over the place about halfway through, and saves Marin in the mountains late in the story. At the very end of the story, if you haven't died, she'll survive the end of Koholint by becoming a seagull, like she wished.