Link goes to Greatfish Isle in search of Jabun, but finds that the island was destroyed and a curse has spread over the seas.
Trade with the Merchant
After the cutscene, cross the beach until you are facing water, and look to your right. There is another merchant there. Trade until you get the Exotic Flower, if he offers it.
Get a Piece of Heart
Next, get back to your boat and turn it in the opposite direction from where it is facing. There is a spiral-shaped island there that has a ramp at the rear of it that you can climb up. Go to the top of the spiral island. You will find a Korok and a withered tree, but you can't help them right now. Keep them in mind for later. Set the wind to NW if it isn't already, then jump off and use your Deku Leaf to glide between two sections of the island. There is a chest with a piece of heart in it on the right side in the cliff wall. After you get it, jump down and swim back to your boat.
Return to Windfall
Before you leave the island, go to the fish guy and get this place marked on your sea chart. Then set the wind to NE and set sail.
On the way to Windfall, you can find Tingle Island, which you can get marked on your chart. There is no need to stop there right now, though.
Windfall
After you automatically land, go up the hill and turn right so that you are facing the bomb shop. Since the front door is locked, go around the side of the building, sidle across the ledge, face the back of the building, climb up the vines, and crawl through the hole.
During the cutscene, they will say a password. If you forget it, just ask your boat.
Before you continue, check the postbox here because you might have a letter or two.
Use the Password to Enter the Pirate Ship
Go up to the gravestone on the northwest part of Windfall and jump onto the pirate ship. Talk to the door and enter the password, making sure to capitalize any letters that were capitalized. If you entered it correctly, you will get in.
You can check out Tetra's cabin if you wish, since it wasn't accessible before.
Pass Niko's Test
Go down the stairs and Niko will be there with another test. When he is on the other side, hit the switch and start jumping across. You will sometimes need to hold down R and change direction in order to get there. Note that the ropes at the left of the room move from side to side, so don't be too hasty. Open the chest on the other side to get bombs. Then watch the scene.
Nintendo Gallery Note: There is no need to take a pictograph of Niko. You will get his figurine when you get Tetra's picture later.
Return to Outset Island
Now go above decks, walk along the prow, jump off onto the grass (or just swim to the nearest shore if you jump or fall into the water), check the postbox, and walk to the pier. Your boat moved there automatically. Equip bombs to one of your buttons. You can press that button to shoot your cannon while at sea. Set the wind SW, and make your way to Outset Island, which is at the southern edge of the map. Don't worry about getting there quickly. The curse will make it stay night time for now.
You can get Cyclops Reef and Stone Watcher Island marked on your sea chart along the way.
When you arrive at Outset Island, the next step is to find Jabun.