Forsaken Fortress
Fishman: He reveals that someone on Windfall Island is a collector of Skull Necklaces.
Contents: Pirate's Charm, Skull Hammer, Heart Piece.
The Forsaken Fortress is an important island in the storyline, being Ganon's base of operations and the holding place of dear Aryll. You'll uncover its contents as the story progresses.
The island itself is heavily protected by searchlights and wall-mounted cannons. In order to gain access, you'll need to destroy the massive door.
Star Island
Fishman: Once you've frozen a monster with an Ice Arrow, you can smash it to bits with the Skull Hammer.
Treasure: 200 rupees, found using Treasure Chart 7 from Windfall Island.
Contents: Heart Piece.
One of the rocks on this island is concealing a secret hole. Bomb it out of the way and defeat all of the monsters in the cave for the Heart Piece.
Northern Fairy Island
Fishman: The shopkeeper on Windfall Island has a special item he calls Magic Armour.
Contents: Treasure Chart 22.
The seas around Northern Fairy Island are watched by an enemy submarine. Inside is a dark room full of nasties. Swing over them all using the laterns hanging from the ceiling, and you'll reach the Chart.
Great Fairy: Rupee upgrade.
Enter the building on the island to be blessed with a larger wallet, allowing Link to carry either 1000 or 5000 rupees.
Gale Isle
Treasure: Triforce Shard 2.
Contents: Hookshot.
Gale Isle is the location of the Wind Temple, in which you can find tasty treasures. The entrance is blocked by a strong wind which will blow away the delicate Link. Wear some heavy boots to resist the gale, and destroy the entrance rock to end it for good.
Crescent Moon Island
Fishman: The Ghost Ship appears here duing a full moon.
Treasure: Heart Piece, found using Treasure Chart 11 from Dragon Roost Island.
Contents: Treasure Chart 9, Treasure Chart 10.
An enemy submarine lurks nearby. Simply light all of the torches inside to gain access to Treasure Chart 9.
Treasure Chart 10, on the other hand, is just waiting in a chest on the middle of the island.
Seven-Star Isles
Fishman: If you're hunting Big Octos, look for flocks of seagulls and head in their direction.
Treasure: Triforce Shard 7.
Contents: Treasure Chart 16.
Bomb all of the cannons protecting the islands and a chest will appear, containing Treasure Chart 16
Big Octo: Heart Piece.
Overlook Island
Fishman: He reveals that the island contains a Triforce Chart, but that you can't land on it.
Treasure: Secret Caves Chart, found using Treasure Chart 13 from Two-Eye Reef.
The Secret Caves Chart is a special map pointing out the locations of all of the caves (holes in the ground) to be found on the Great Sea. Note that this chart doesn't keep track of which ones have been visited, nor does it reveal anything about their contents.
Contents: Triforce Chart 8.
With nowhere to land, the only way to reach Overlook Island is hookshotting onto the palm tree. The cave has a room with five doors, the central one opening only after defeating all of the enemies behind the others. Inside is Triforce Chart 8. Note that the central room will be defended by 4 Darknuts once the other enemies are slain.
