After getting the Triforce Piece from Dungeon 6, get the monster bait and go to Dungeon 7.
Get the Monster Bait
To get through the next dungeon, you are going to need Monster Bait. With the Whistle, you can warp to any of the previous dungeons you completed. This makes it easy to reach the shop that has the best price for Monster Bait. See Using the Whistle for information about how the whistle works.
Use the Whistle to warp to dungeon 3. If you don't understand how the whistle works, just face north or west and use the whistle, let the whirlwind catch you, then if you aren't in front of dungeon 3 after that, use the whistle again. Repeat until you are in front of dungeon 3. (If you aren't sure which dungeon number it is, just go inside and see what it says in the top left corner of the screen.)
Once you have arrived in front of dungeon 3, go west, north, east, and north. Keep going north until you reach a dead end. Touch the top middle statue to make it start moving, then go down the stairs. Buy the Monster Bait for 60 rupees.
Go to the Dungeon
From the place where you got the monster bait, go south twice, west, northwest, and north. Then use the Whistle to reveal the dungeon entrance. If you are not at the place where you got the Monster Bait, then use the whistle to warp to dungeon 3, then go west, north twice, northwest, and north, then use the whistle to reveal the dungeon entrance.
Go east from the entrance and kill the Moldorms to get bombs.
Get the Compass
Go north from the Moldorm room and use the Blue Candle to light it up, then bomb the middle of the north wall and go through the hole. Use the Blue Candle to light up this room. One of the Stalfos is carrying the Compass. Kill it to get the Compass.
Optional: Get More Bombs
Go south from where you got the Compass and use the Blue Candle to light up the room, then go east. Go east again to reach a room with a Digdogger. You can kill it (use the whistle first) to get more bombs.
Optional: Get a Key
Go east from the Digdogger room. One of the Stalfos is carrying a key. Kill that Stalfos to get the key.
Get More Bombs
If you are in the room where you got the compass (with two strips of water in it), go south to the dark room and light it with the Blue Candle, then go west. Kill the blue Goriyas to get bombs.
If you are in the room where you got a key (with one strip of water in it), go west until you reach the dark room and light it with the Blue Candle, then go west. Kill the blue Goriyas to get bombs.
Get Even More Bombs
Bomb the middle of the west wall and go through. Be careful of the spiked traps around the walls. Kill the Keese to get bombs.
Get a Second Key
Go south to get another key, but be careful of the ropes, and the fireballs from the statues.
Optional: Get a Blue Rupee
Go north until you reach a room with three Dodongos. If you kill them, you get a blue rupee.
Unlock the north door in the Dodongo room and go through it to increase your bomb capacity for 100 rupees. You will now be able to carry 16 bombs.
Get a Third Key
Back in the room with the three Dodongos, go east. Then in the room with the red and blue Goriyas, go north. Kill the Goriyas and Keese in this room, avoiding the floating Bubbles, which will make you temporarily unable to use your sword. Once you kill the Goriyas and Keese, the north door will open. Go through.
Kill or ignore the Digdogger (use the whistle first if you want to kill it) then bomb the middle of the east wall and go through the hole. Kill the Moldorms to get a key.
Get Blue Rupee
Go west from the sandy room until you reach a room with red and blue Goriyas. You can kill all the Goriyas to get a blue rupee.
Feed the Monster
Go north through the locked door. You will find a Goriya grumbling at you. Equip the Monster Bait and use it. The monster will disappear. Go north.
Get the Map
In the room north of where you fed the grumbling Goriya, use the Blue Candle, then get the Map.
Get a Blue Rupee
In the room where you got the map, bomb the middle of the north wall and go through. Collect the rupees, then bomb the middle of the east wall and go through. Kill all the Goriyas here to get a blue rupee. The doors will also open.
Get a Fourth Key
Go east through the door that opened, get the key, then kill all the Goriyas to open the door.
Get the Red Candle
Go west, then south, then bomb the middle of the east wall and go through. Kill all the Goriyas, then push the leftmost block up or down and go down the stairs in the middle. Get the Red Candle. It does the same thing as the Blue Candle, but you can use it as many times as you want per screen.
Go to the Dungeon Boss
Go back upstairs and bomb the middle of the east wall. Go through. If you kill all the Goriyas here, you will get more bombs. You can also go through the north door and kill the Moldorms to get more bombs. If you do, go south to return to the previous room.
Go east through the locked door. You will have to kill the Digdogger to proceed, so use the whistle and kill the small Digdoggers that appear. Then the north door will open. Go through.
You can optionally kill the Dodongos here to get more bombs. Then bomb the middle of the east wall and go through.
Quickly go to the center of the room to avoid getting grabbed by a Wallmaster. Then carefully touch a wall to make a Wallmaster come out, and kill it as soon as possible. The Magic Wand will help a lot here because it will still work even if a floating Bubble touches you. Keep touching the wall and killing Wallmasters until no more Wallmasters appear when you touch the wall. Then push the block in the middle of the right side of blocks to make the stairs appear. Go down the stairs and follow the passage until you are upstairs again. Bomb the middle of the east wall and go through to reach the dungeon boss.
Hit Aquamentus's horn to injure him. Once he is dead, take the heart container and go east to get the Triforce Piece.