Leave the ledge (you can jump into the water for no damage, amazingly) and go to your grandma’s house. Inside, you’ll find her curled up in a chair, delirious about you and Aryll going missing. Equip the bottle with the fairy in it and use it.
It will heal you and your grandma, releasing her from her delusions. She wants to help in some way, and does so by filling your empty bottle with Link’s favorite soup - Elixir Soup !
Secondly, it DOUBLES the power of your attacks until you take damage - essentially meaning that you could go on for virtually forever with double power if you are good at defense. Thirdly, and this is the best part, the bottle is so full that you can use the Elixir Soup TWO times! As the game says, that is one hearty soup!
After obtaining your Elixir Soup, exit your grandma’s house. Go back to the King of Red Lions. Sail around to the back of the island; it is recommended that you save.
As you sail around to the back, you’ll find that there is a massive whirlpool there. If you’ve ever fought one of the Big Octos, you’ll recognize it. However, the challenge is not to defeat a Big Octo, but to break down a stone wall with Bombs! Equip the Bombs and aim towards the wall. If you haven’t yet upgraded your Bombs, or are a bad aim, wait until the boat is close to the cracked stone wall. Aim at the upper area of the wall and fire.
If you hit the correct area, it will flash red - you can only destroy the wall from top to bottom, and there are three sections in all. It will take one to three (?) shots to destroy each section. If you take too long and get sucked into the center of the whirlpool, you’ll have to start all over with a limited supply of Bombs, I believe.
Inside, you’ll see nothing. However, as you travel in, the water begins to ripple and swell as a massive thing rises to the surface - Jabun. Exit the cave when you are ready.
Upon exiting, you are able to place the three pearls on their islands. However, I recommend doing a few side-quests, if just to upgrade some items and hearts!