The Zora Armor is a tunic featured in The Legend of Zelda: Twilight Princess that the protagonist Link can don. Like the Zora's Tunic of The Legend of Zelda: Ocarina of Time, it'll give the player complete control under water and will even allow him to breath as he would if he was on ground. Link will come in possession of this suit when he brings Prince Ralis, Queen Rutela's son, back home safely. The queen will reward Link with this suit after ultimately, and deliberately, dying.
If Link wishes to walk on the sea floor without drowning, then he can also place the Iron Boots on his feet in combination of the Zora Armor. While wearing this suit, Link will become more vulnerable to fire and ice based attacks.