The Legend of Zelda/Underworld/Quest 1/Dungeon 3

Objectives

The entrance to this dungeon is located at the bottom left corner of section 6. Approach it from the area to the west.
From the entrance, go left and clear this room and the above to obtain two keys.
Move up to the next room above. The right wall can be bombed to expose a hidden passage that can serve as a signifigant shortcut to the end of the dungeon.
Proceed left to the next room to obtain the compass.
From the compass room, enter the left room, and then the room below to locate a stairwell. Down these stairs, you will find the raft.
From the raft room, move up two rooms, and two rooms to the right and end up in a room with four doors.
From here, the pathway above is optional if you wish to obtain information about the location of the White Sword. If you enter the room above, open the north door by pushing the left block. Enter the room to the left of the man to obtain a key.
From the four door room, head right to next room and obtain the map. You can bomb the right wall to expose a shortcut to the dungeon boss.
Otherwise, from the map room, head down to the room below, clear it of the Dakrnuts, head right and defeat the Keeses and Zols, and open the door above.

The boss is a Manhandla. To defeat it, you must remove all four claws. You can do so by stabbing each one individually, but it's faster to place a well timed bomb that explodes on the center of the body, eliminating all four claws at one time. Since Manandla moves unpredictably, it takes a little luck to drop the bomb at just the right place.
Defeat it to earn a heart container. Continue on to the room above to obtain the third piece of the Triforce.