The Raft is an obtainable item in The Legend of Zelda and The Adventure of Link. This item is used by Link to travel across large bodies of water, like a lake. It is found in the third dungeon of The Legend of Zelda, Level 3: The Manji, and in the third palace of The Adventure of Link, the Island Palace.
The Legend of Zelda
The only use of the Raft in The Legend of Zelda is to travel across large bodies of water to reach the other side. This can only be done in two locations, and they are both shown below.
Level 4: The Snake
The Raft is required to reach Level 4: The Snake, as it is found on a little island that is found in the middle of the large lake in the middle of Hyrule. If Link walks up to the dock in the screen right below the dungeon, he can walk off and the Raft automatically takes off and sends Link to the entrance to The Snake.
On the other side of Hyrule, there is also a small island that is seemingly unreachable. However, Link can use his Raft again and he is sent right to this island. On this island, there is an entrance to a cave that looks very much like a dungeon. Inside, the Old Man offers Link a Heart Container and a 2nd Potion. He says to choose anyone Link wants. This is one of four of such locations.
The Adventure of Link
Breath of the Wild
The Raft makes a return in Breath of the Wild, but this time, it is not a usable item. Instead, they can be found all over Hyrule, by lakes, oceans etc. Link can use the Raft in conjunction with a Korok Leaf in order to control the raft and move in a desired direction.