Follow the path around the right side of the wall and go up the stairs till you see King Zora. Speak with him and he will say something about his daughter, Ruto. Go through the small tunnel to your left and talk to one of the Zora's. He will ask you if you would like to play his diving game. After paying him, dive into the water and collect all of the rupees before the time limit is up. If you win, go back and talk to him again. You will receive the silver scale, which will allow you to dive longer. Re-dive and find a small opening under water. Dive thru and you will be warped to Lake Hylia. There, you will find a bottle under water. Lock on and dive down to get it. The bottle contains a note from Princess Ruto. Dive back through the warp point and show the bottle to King Zora. Before going to Zora's Fountain, go down to the water and catch a fish in a bottle. He will move, allowing you to go behind the throne. Walk along the path to your right, and walk through the dark tunnel. This will lead you to Zora's fountain.