The King of Red Lions will inform you that Ganondorf has vanished and will ask you to gather all eight shards of the Triforce. Those shards can be found in any order once you have the Hookshot.
To begin with, you will have to find the eight Triforce Charts. Open the IN-credible Chart from your inventory to see their location.
Triforce Chart no 1 - Islet of Steel
Head for the Islet of Steel (B5). Get inside this metal structure while avoiding or destroying enemy ships with bombs. Inside, stand on the wind symbol, play the Wind's Requiem and open the chest.
Triforce Chart no 2 - Private Oasis
If you don't have the Cabana Deed yet, go back to Windfall Island, get in the school, speak to Mrs. Marie and give her 20 Joy Pendants (more details by clicking on the object). Then, sail to the Private Oasis (E5), go towards the Cabana and show the deed to the "human" door. Use the Grappling Hook on the bar on the ceiling to put out the fire from the fireplace, then jump down the hole in the hearth. Go forward, then right and go down the ladder. Crawl into the passage right of the ladder. Turn right, then go on straight ahead to the exit and climb up the ladder.
Hammer down the left stake with the Skull Hammer, go around the wall behind the spikes and climb down the ladder. Take the path facing the ladder and climb out at the very end. Go across the room, then jump down the hole (without a ladder). Get rid of the Gibdos then break the pots, crawl into the passageway and climb the ladder. Play the Wind's Requiem on the symbol and open the chest. Hammer down the stake, along with the next one, and go back to the entrance. Leave the Cabana and the Island.
Triforce Chart no 3 - Bird's Peak Rock
From the last island, keep sailing east until Bird's Peak Rock (G5). Land on the lower island and use the Grappling Hook on the bar to reach the top. Then take out a Hyoi Pear (you'd better have a lot of them) and a seagull will come to eat it. As the seagull, the safest solution is to fly towards the condors' nests to draw them at you then to fly towards Link and take back his control. As Link, get rid of the condors, then use another pear. Lead the seagull towards the nests and make it bump into the five switches to open the door on the island. Jump into the hole behind the door and play the Wind's Requiem on the symbol.
Triforce Chart no 4 - Diamond Steppe Island
Head for Diamond Steppe Island (A6) and use the Hookshot at one of the palm trees to get on it. Use the Hookshot again on more palm trees to reach the summit and jump into the hole. Get into the warp pot, then into the one in front of you, then into the right one at the back of the room. Walk across the room, jump into the left (diagonal) pot, and finally open the chest to get the Ghost Ship Chart. Having this map in your possession will now make the Ghost Ship visible, and it shall appear on your Sea Chart. If you need, play the Song of Passing so it's night-time (or wait for the sun to set), take a look at the map and get to the place it is according to the current moon phase. Wander around until you find it and go straight ahead to get on board. Get rid of the Wizzrobes and the ghosts, then climb the ladder, play the Wind's Requiem on the symbol and open the chest.
Triforce Chart no 5 - Needle Rock Isle
Go north-west of this region (A5). You will see three boats, including a golden one. Destroy it with your bombs, then use the Grappling Hook to pick up the chest where it sank.
Triforce Chart no 6 - Outset Island
Go back home (B7), go behind your grandma's house and climb on the ledge. There, use the Hookshot on the tree all the way to the top, then lift and throw the Headstone away to jump into a hole. Shatter the pots to catch up to three fairies in your bottles, then jump into the next hole. Fight off the Keeses, then the small devils and numerous waves of monsters until a "break" room with pots and a light beam allowing you to get back on the surface. Shatter the pots to refill your hearts and rupees, then continue your descent for around thirty rooms with an increasing difficulty of enemies (and another "break" room). Finally, play the Wind's Requiem on the symbol and pick up the chart from the chest. Before going back to the surface, you can reflect the light at the stone statue and go through another twenty rooms to get a Piece of Heart.
Triforce Chart no 7 - Headstone Island
Go to Headstone Island (C5) and lift the huge headstone. Jump into the hole and open the different doors to fight the enemies in the different rooms. Get rid of another two Darknuts in the middle room, then open the last door, play the Wind's Requiem on the symbol and open the chest.
Triforce Chart no 8 - Overlook Island
Now it's time to go to Overlook Island (G1) all the way up to the north-east of the Sea Chart. From your boat, aim your Hookshot at the tree the furthest to the north, then at the remaining trees to find a hole and get into it. As for the previous chart, fight the waves of enemies in the four rooms, along with the middle one, then play the Wind's Requiem in the last room to get the Sea Chart number eight.
Now that you own all eight Triforce Charts, you can go to Tingle Island (C3). But before this, you will have to gather at least 3184 rupees! On this island, climb the ladder and talk to Tingle (wearing green). He will detect your charts and offer you a deciphering service for 398 rupees per map. Once a map got deciphered, the position of the Triforce Shard will be marked on the IN-credible Chart along with a more precise location on the deciphered chart.
If you don't have enough rupees, have as many Sea Charts deciphered as you can before coming back later. Finally, head for each shard location and recover the chest with your Grappling Hook. You can also use the light auras marking the chests' location to help you.