Zora's River
Go forward and you will soon meet the owl again. After taking good note of his advices, blow up the rocks in front of you and meet the Magic Beans Salesman. Buy some from him if you want to, you should buy 10 of them as young Link and plant them in soft soil like next to the Salesman. Cross the river where it's making a right angle, then go left, follow the path going upwards, jump down and climb on the tree branch in the water. You will see some frogs, play the ocarina for them and they will reward you with a purple rupee (50 rupees) or other rupees. Then keep going north until you reach the waterfall. On the right, you will see a shortcut to the Lost Woods (you can use it only after getting the Silver Scale). Stand on the Triforce symbol in front of the waterfall, play Zelda's Lullaby, then jump forward.
Zora's Domain
Go right and go up the path. Speak with the Zora King, whose daughter has disappeared, then go left, talk to the Zora and pay 10 rupees to take part in a game. You have to win a diving game to get the Silver Scale. When you have it, dive once more, look for a passage underwater and get in.Lake Hylia
Look at the bottom of the water to find a Bottle. Pick it up then use the underwater tunnel again. If you want to visit Lake Hylia and its surroundings, DO NOT talk to the owl, because he would bring you back to Hyrule Castle.
Zora's Domain
If you have an empty Bottle, catch a fish located north-east on the map. Go back to the King and bring him the letter from the Bottle. He will entrust you with the mission to save Princess Ruto. If you don't have the fish yet, go catch it now, then take the path to the right and go behind the King.
Zora's Fountain
Go ahead and swim until you reach a small island on the right (south-east of the map), then drop a bomb next to the grey rock. Get in the Great Fairy's Fountain and receive Farore's Wind. Now go in front of the big fish Jabu-Jabu, give him the fish from the bottle and you will be swallowed up!