The Zora Armor is a returning important armor piece in The Legend of Zelda: Tears of the Kingdom. It is an entirely unique item that will allow you to swim up waterfalls, which is incredibly handy when in the Lanayru region of Hyrule. In fact, it is considered mandatory if you want to complete the Water Temple. To get it, you will need to do a quick side quest. Here is how to complete Restoring the Zora Armor in Zelda Tears of the Kingdom.
How To Get the Zora Armor in Zelda Tears of the Kingdom

To get the Zora Armor in Zelda Tears of the Kingdom, you must finish the Sludge Covered Statue main mission. Once this is done, Yona can be found in the bath area beneath the throne room in Zora’s Domain. Talk to her, and she will let you know she is working on fixing your Zora Armor, but she needs a rare fish to do it. You need to find an Ancient Arowana. For a hint, you can talk to the Zora blacksmith, Dento.
Dento will let you know he saw an Ancient Arowana near Mipha’s Statue at the peak of Ploymus Mountain. If you have already talked to Sidon, you can fast travel to the Ihen-a Shrine for a quick trek up the stairs. There is always at least one of these fish in the pool below the Mipha statue.
There is always a chance that you already have an Ancient Arowana. While the Mipha statue is the only place we have seen them appear on the surface, they can be found regularly in water sources in the sky islands. Look for them around Great Sky Island and North Tabantha Sky Archipelago.
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Once you have gotten the Ancient Arowana, return to Yona and give her the fish. That is how to complete Restoring the Zora Armor in Zelda Tears of the Kingdom. She will reward you with the Zora Armor. As mentioned above, this unique armor will allow you to swim up waterfalls. If you are in the water at the base of a waterfall, press A to ascend it. If you are paragliding, you will automatically start going up it when you make contact with the water.
Wearing the Zora Armor and the other Tears of the Kingdom Zora Armor set items will also increase your swim speed. If you wear all three simultaneously after upgrading them twice at a Great Fairy, your swim dash speed will also increase.