After you visit the Fairy of Power, you should head over to Zora's domain. On the world map, it is in the northeastern section. A river flows into it, so follow the river to get in. You will meet the Owl again and you will have to destroy the large boulders blocking the way to enter the outer part of Zora's domain. After this, you will see a fat kid sitting on the ground in front of a fence. This kid will sell you what are called "magic beans." Plant these beans in those patches of soft soil that you may have been seeing. An example of this soil patch is right next to the fat kid. When you plant the bean, in seven years it will grow into a floating leaf that may either make your trips easier or bring you to secret places.
You will notice a chicken running around. You will need the chicken to float across the river in different parts in order to advance. The chicken is also very useful in obtaining the two pieces of heart that are on ledges. If you follow the river upstream, you will eventually come to a waterfall. You will see the crest of the Triforce in the ground right in front of the waterfall. If you play Zelda's Lullaby here, the waterfall will stop and give you access to the important part of Zora's Domain. Your first order of business is to win the Silver Scale.
To do this, you must take part in a diving contest and collect the blue rupees, which are underwater, by diving below the surface to collect them in a limited amount of time. If you do this in the allotted time, you will receive the Silver Scale, which allows you to dive underwater and to hold your breath for a much longer time. Now, in the huge pool in Zora's Domain, you may notice what looks like a door under the water. Dive down and go through this door. You will emerge in Lake Hylia. Refer to the Bottles summary to help you find the bottle on the bottom of the lake with the letter in it. Bring this bottle back to Zora's Domain by diving underwater and going back through the door in Lake Hylia. You must "use" this bottle on King Zora with a "C" button to show him the letter in the bottle.
When he reads the letter, he will move aside to give you access to King Zora's Fountain, which was previously blocked by his massive body. However, before you go there, you must trap a fish in this no-empty bottle. Go back into the pool in the middle of Zora's Domain, and search near the shallow areas for big, blue fish. Swing the bottle around with the "C" buttons to trap it. Now, proceed to Zora's Fountain with the fish in the bottle. In the middle of Zora's Fountain, you will see a monstrous fish. His name is Jabu-Jabu. In order to get him to open his mouth, you must "use" the bottled fish on him. He will smell the fish and open his mouth to suck it in, along with you. You have now entered Jabu-Jabu's Belly, which is covered in the next section.
Proceed to Inside Jabu-Jabu's Belly...