Dark Link appears, and in beating him, Link rejects that version of himself.

Link wandered around the strange room that seemed to go on forever, unsure what to do next...until the foe appeared. It looked like Link's normal body, a Hylian male, down to the exact details, with one exception. It was a dark black, like a shadow, and with blood red eyes. It stared at Link, and when he tried to make a move, the other Link mirrored it. Unsure about fighting a copy of himself while in this body, Link considered taking the mask off.

But then, he rejected that idea. Become that uncouth oaf, just to fight a copy of the same body? No. That wouldn't be the best idea. After all...it seemed as though Princess Ruto liked him in this form. Changing it without her permission would be a grave mistake. The more Link looked at this dark reflection of his 'normal' body, he became angrier. Was this shallow imitation accurate? Did he truly look so foolish and unattractive? What had Princess Ruto ever seen in such a vulgar form?

The fight began, and at first it seemed the Dark Link had the advantage. His strength, his reach, those were what he had over Link, so long as he remained in this Zora form. But as they fighting continued, Link started pulling ahead. In this body, he was faster, he was more nimble...and he was a smaller target. After a long and exhausting fight, the Dark Link recoiled back from a final blow and sank into the water, disappearing forever.

With that victory, Link felt like a new person. A better person. She'd defeated the darkness that represented her old form, and felt even more comfortable as a Zora now. But she didn't have time to stand around and pontificate, her princess needed her, and so off she went, to clear out the temple and save the Zora people.