Needle Rock Isles (A5 on the worldmap) is one of The Legend of Zelda: The Wind Waker's 49 distinct islands. Its name is derived from the fact that a spear shaped rock juts out in the center of it. Five sidequests can be completed here.
The first of the sidequests is the only one that you are required to partake in. You'll probably notice the many enemy ships surrounding the island. Destroy all of them to reap a multitude of rewards, though the one you should focus on is the golden one - after destroying it and claiming the treasure that was inside you'll come in possession of the Triforce Chart #5. The other ships that you destroyed will give you an Orange Rupee and a Purple Rupee.
The second sidequest will nab you a Piece of Heart (#10). On top of the needled rock you'll notice a switch, though there's only one way to hit it. Use a Hyoi Pear and take control of a seagull when it comes, then make it hit the switch. After that, the fire that was consuming the treasure chest will die down and you'll be able to take the contents within, which as stated was a Piece of Heart.
Use Treasure Chart #28 to get the Silver Rupee in the ocean. The Orange Rupee can be found by using a fire arrow to melt the iceberg. Drop in the recently revealed hole and light all of the torches on fire to reveal a chest with the said Rupee inside. The last sidequest is to poor the special type of water on top of the Korok's seedling to cause a future forest to start.