After the events of Generic Quest, Link and Zelda sailed back to Hyrule on a raft. However, the Triforce Link picked up after slaying Ganon rose out of nowhere and struck his raft! It turns out Ganon used the Triforce as a Horcrux-type thing, and it brought him back to life. Oh, and he kidnapped Zelda, too. Fantastic.

Link washes up on Mirago Island (but he only finds out this name when an old man in a cave tells him), and his raft's destroyed. Even if he obtained another one (which he does, mind you), he wouldn't be able to escape without Zelda because Ganon casted a spell around the island that created a barrier disabling any entry or exit. Also, leaving Zelda would give him stress problems, and we don't want that, now do we?