You've now entered the Zora’s Domain. There is a sidequest you can do:
And there is one more sidequest, although it’s not really a sidequest, because it is necessary to do to complete the game:
After you’ve obtained the scale, go down into the pool in the Zora’s Domain, and try diving deeper. Down there, you’ll notice a passageway which you can now swim into, so do so.
Now your in Lake Hylia. There are a few more sidequests you can complete:
Most important, in Lake Hylia you will find an “Empty Bottle” at the bottom, right out side the entrance. Just dive to reach it. This “Empty Bottle” actually contains a letter to the Zora King from his daughter, Princess Ruto, so return the letter to him to proceed. Not to mention you get a free bottle!
Finally, after he takes half an hour to move his fat ass out of the way, you can head ‘round back to the Zora’s Fountain.
In order to get Lord Jabu-jabu to open his mouth you’re going to need to offer him a fish. A fish can easily be found floating around in the shallow water in the Zora’s Domain, just outside the store. Snatch one with an empty bottle and then drop it in front of Lord Jabu-jabu.
Welcome to the next dungeon, Inside Lord Jabu-jabu's Belly.
