Like its predecessor, Tears of the Kingdom is packed to the gills with hidden treasures to discover dotted throughout the map. These treasure hunts are taken a wonderful step further in TOTK with the inclusion of intricate cave systems for you to go spelunking in.
One such cave must be explored as part of the Secret Treasure Under The Great Fish quest, giving you a helpful reward that may awaken many memories of the past. Riddles can be a bit tough to decipher sometimes, so we'll lay it out in detail for you here.
How To Complete Secret Treasure Under The Great Fish
Though you can find the treasure itself without it, to first acquire the Secret Treasure Under The Great Fish quest, you must complete the Regional Phenomena quest of Zora's Domain, as Sidon is the one who offers you the quest.
Upon talking to him, he informs you of an old riddle that hides the location of a great treasure. The riddle is as follows:
"The great fish. The eternal guardian. A secret treasure awaits just beneath the stony form of its statue. Below the long bridge that reaches for the statue, leave your fears behind. Pass beneath two waterfalls to find your prize."
There are only two great stony fish in Zora's Domain, the Floating Scales Island and the Stone Fish that sits atop Zora's Domain's throne room. For the quest, the latter is what we're focusing on.
Though it says a great treasure rests beneath its form, you must first find access to it rather than simply searching under the throne room.
To do this, we must first go to the Great Zora Bridge, the 'long bridge that reaches for the statue' mentioned in the riddle. However, there is only one waterfall visible here.
The second waterfall is hidden inside a cave. Pass beneath the waterfall that climbs directly to Zora's Domain, and you'll find the entrance to the aptly named Cave Under Zora's Domain.
Though it can be tempting when surrounded by all these waterfalls, it's better not to wear the Zora Armor here as it will make you automatically ascend the waterfall, making entry impossible.
This opens up into a large cavern housing a chasm to the depths and, you guessed it, a second waterfall.
Same as before, pass beneath this waterfall, and you'll enter into an even smaller room with a chest sitting on an elevated platform.
Within it, you will find the Vah Ruta Divine Helm, the helmet of the Champion Mipha from Breath of the Wild. It offers increased swim speed and bittersweet memories of the past.
The exact coordinates of the Cave Under Zora's Domain are 3240,0373,0079, for those who want to get there quickly.
With that, The Secret Treasure Under The Great Fish is complete. Return to Sidon to get some well-deserved praise for finding his sister's old headgear.