Zelda Tears of the Kingdom: Shrine Guides and Fan Builds.

To complete the Secret Treasure Under the Great Fish quest in Zelda Tears of the Kingdom, players must first complete the Sidon of the Zora main quest and talk to Sidon in Zora's Domain. They should then follow a long bridge to a waterfall, jump down and swim to the back side of the waterfall to enter the Cave Under Zora's Domain. After gliding to the opposite side of the hole leading down to the Depths, players will find themselves in a chamber with a chest containing the Vah Ruta Divine Helm. It is important not to wear the Zora Armor Set during this mission.