Grappling Hook

From Zelda - Wiki on Neoseeker

The Grappling Hook is one of the most versatile items in The Legend of Zelda: The Wind Waker, as it allows Link to swing between ledges, snatch loot from enemies, and pull up treasure from the depths of the Great Sea. It is acquired from within the Dragon Roost Cavern on Dragon Roost Island.

Enemy Treasure

Most enemies will have certain items that can be stolen from them with the grappling hook before they are disposed of. These items will be placed in your Spoils Bag. A list can be found below:

Item	Enemies
Chu Jelly	ChuChus
Joy Pendants	Bokoblins
Boko Baba Seeds	Boko Babas
Golden Feathers	Peahats, Kargoroks, Mothulas
Skull Necklaces	Moblins
Knight's Crests	Darknuts

Sea Treasure

When the grappling hook is used on your boat, it will automatically be attached to a winch and crane, which allow you to pull up treasure from the sea. If you see rings of light out on the ocean, sail over to them and lower your hook. Usually you will pull out Rupees, but occasionally you will find a Piece of Heart. They are found all over the Great Sea, but are more common at night, or in the reefs. You can tell when you are in the right spot by looking closely or by listening to the sparkly sound they make when you are near. Another way of finding treasure is to use Treasure Charts, which are identified by large beams of light that shoot up into the sky instead of tiny rings.