‘Sidon of the Zora’ quest walkthrough in Zelda: Tears of the Kingdom
How to find Sidon and complete the “Sidon of the Zora” and “The Sludge-covered Statue” quests in Zora’s Domain.
This article references relevant content from the polygon.com website. Original article link: [https://www.polygon.com/zelda-tears-of-the-kingdom-guide/23705884/sidon-of-the-zora-walkthrough]

In The Legend of Zelda: Tears of the Kingdom, after getting acquainted with Purah and she catches you up to speed, she’ll send you off in four directions as part of the Regional Phenomena quest, with the eastern point being Zora’s Domain.
For those familiar with the original, you’ll know this to be the home of Sidon and the other Zora people. Once you arrive and start the “Sidon of the Zora” quest, it’ll then encompass many objectives - including “The Broken Slate”, “Clues to the Sky” and “Land of the Sky Fish”.
After those, we have guides on how to complete the Ancient Zora Waterworks, Wellspring Island, and the Water Temple separately, since those are their own beasts, bringing the Zora region’s main questline to completion.
How to reach Zora’s Domain and starting the ‘Sidon of Zora’ quest
There isn’t a specific way to get to Zora’s Domain this time around, as you can trek up the mountains, take the paths up alongside the lanterns, or glide in (if you have any Skyview Towers nearby unlocked).
The one overlooking Zora’s Domain is Upland Zorana Tower is closest, though cannot be completed until you have an armor piece from this quest. That said, it can offer a useful reference point:

How to start the Sidon of Zora quest
Once you get to Zora’s Domain, talk to the marked stingray-head Zora below:

She’ll lament the muddy statue in front of her, so use a splash fruit to wash the mud off the statue. This will both instantly complete “The Sludge-Covered Statue” and start the “Sidon of the Zora” quest.
Helping Yona repair the armor and finding Sidon
After introducing yourself to Sidon’s fiancé, Yona, she’ll tell you to meet her at the infirmary, if you have time, which you should definitely do. She’ll have your Zora Armor waiting, but first you’ll need to give her an ancient arowana.
She notes that the blacksmith downstairs knows where to find one, but we recommend grabbing one from the ponds on the Great Sky Island (where you started off in the game). We found plenty in the small floating ponds north and east of Nachoya Shrine. Both of these are outlined in more detail on our ancient arowana locations page.

Once you have the Zora Armor, equip it and now you’ll swim up waterfalls. You can use this to easily access the Upland Zorana tower to the west, or head straight to Sidon in the north. Just swim up the waterfalls at Mikau Lake and Lulu Lake (east of Zora’s Domain) to end up at Mipha’s Court.
Make sure to complete Ihen-a Shrine nearby so you can easily fast travel back to this location.
From here, it’s time to find Toto Lake for “The Broken Slate” quest.