When Link first enters Great Bay, he finds a dying Zora named Mikau floating near the shore. Gerudo Pirates fatally wounded him when he attempted to rescue the eggs of a fellow band member named Lulu. Link pushes him towards the shore, but his wounds are too great. Mikau summons the strength to play one last song explaining his dilemma and then asking for someone to rescue the eggs and to heal his soul.
Link plays the "Song of Healing" giving Mikau a vision of him and Lulu joining the band. Mikau then disappears, leaving behind the Zora Mask imbued with his spirit. Link takes the mask with him, and whenever he puts it on, he transforms into Zora Link, which appears to be a combination of Mikau's body and his own. Link is able to impersonate Mikau while in his Zora form, which allows him to help The Indigo-Go's and their singer, Lulu. When Link tries to play his Ocarina of Time while wearing the Zora Mask, it manifests itself as Mikau's Guitar of Waves.
As a Zora, Link's ability to swim is tremendously increased, and he is able to breathe underwater and sink to the bottom of a body of water to perform terrestrial actions such as walking (although his evasive side jumps and back flips suffer due to the water's density). His offensive capabilities include acrobatic punches and kicks, using a pair of fins on his forearms as both short and long-range weapons (of similar purpose to the Sword and the Boomerang, respectively), and on land, the ability to perform a somersaulting kick attack, that serves as a slightly slower equivalent to Link's Jump Attack.
Pressing R while on land causes Zora Link to hold one of his arm fins up, allowing him to use it much as he would a shield. While doing so, Link can press B to surround himself with an effective bio-electric barrier, which has both offensive and defensive properties. When most enemies touch him while in this state, they will either sustain damage or be stunned temporarily. While swimming, the bio-electric barrier may also be used simply by pressing the R button, allowing Link to swim undeterred by enemies. The barrier can also be activated while being held by certain enemies, such as Dexihands, Like Likes, and Majora's Wrath. This deals damage to the foe and frees Link from their grasp. Maintaining the barrier gradually depletes the Magic Meter, and when fully drained, it cannot be used until the meter is restored. As a Zora, Link is more vulnerable to fire and ice attacks. If hit by either, the screen will fade to black, and Link will be reset to the entrance of the room in a similar manner to when he falls into a bottomless pit.
In the 3DS version, Zora Link's swimming is slower; the bio-electric field also acts as a speed boost, allowing him to swim faster while the field is up.