He turned into a non-descript female zora.

...the mask immediately latched onto his face, sealing itself to him. Link felt magic pouring into him, and knew his body was changing. He was screaming in pain, which was so excruciating that he couldn't feel his body at all, the only thing he could feel was the pain. After a few seconds it faded, and Link could see clearly again. He was still a little numb, but he could feel enough to know that something was wrong. He looked down to see a naked, female Zora. His entire body was covered in light blue scales, and his body had a slight hourglass shape to it, with modest breasts and a curvy backside. Reaching up to his head, he found that he had grown the same long, tail-like extrusion on the back of it that most Zora had. Link looked at his feminine, webbed fingers, unsure how to feel.