After you help the ghost find its home and its grave, you go to Martha's Bay and dive into the Catfish's Maw.
Get the Compass
Go west from the entrance until you reach a room with a locked door. Kill the four Keese that are hiding on the four statues, and kill the Helmasaur by hitting it from behind. Then go west through the door that opens.
There is a chest in this room. Open it to get the Compass.
Get a Key
Go down the stairs in the room where you got the Compass.
When you stand on the chain platform, the other platform rises. Quickly jump from one platform to the other when they are close to each other, then jump to the left side and go to the next room.
Step on the platform on the right, then quickly jump to the next platform. Continue jumping to reach the left side of the room. If you need to try again, just go to the right, climb up, and go to the left to try again.
After you reach the ladder in the leftmost room, go up.
Kill the Stalfos in this room, then break all the crystals. Then push the upper blocks toward the middle of the room to form a square. A key will fall from the ceiling. Take it.
Get the Stone Beak
The room to the west is empty right now, so ignore it. Go back the way you came until you are in the room with the locked door. Unlock it and go through.
Go west and kill the Helmasaurs to make the doors open. Go through the west door.
Kill the Helmasaurs in this room to make a chest appear. Open it to get the Stone Beak.
Reach the Mini-Boss
Go east from where you got the Stone Beak, then go east again to a room full of crystals. Go north to another crystal room. Kill all the Stalfos to open the north door. If you talk to the owl statue, it tells you to use a bomb on the skeleton. Go north.
Master Stalfos 1
Hit the Stalfos with your sword. You have to hit it from the right side because it holds its shield on the left. Try hitting near its head or sword arm. You might need to wait until after it has swung its sword, then hit its right side. When it collapses, put a bomb on it. The bomb will damage it.
Eventually, Master Stalfos runs away. Go east.
Reach the Mini-Boss a Second Time
If you open the chest in this room, you find a note from Master Stalfos that says that he stole the treasure from inside it.
Ignore the stairs for now and then go north. Push the middle block up. Then go west, but go east again to return to the room where you pushed the block. Now push the middle block to the right. Go north and step on the switch, then go north.
If you need bombs, jump over the gap, then go east over the gap and go to the next room. There are some bombs there.
Then return to the room with the switch and the five blocks in the middle. Step on the switch again if necessary, then push the middle block down. Go east to the next room.
Master Stalfos 2
Master Stalfos is here again. Fight him the way you did last time. He runs away again.
Reach the Mini-Boss a Third Time
Go back to the previous room. Push the middle block to the left, then go north.
Jump over the gap, then go north to the next room. From there, go west.
Kill all three of the green Zols in this room. One of them is on the other side of the blocks. You can push a block to the side to reach the other half of the room. For example, the block that is three blocks down from the north wall can be pushed left.
Go through the door that opens.
Master Stalfos 3
Fight Master Stalfos like you did before. Again, he runs away.
Get the Map
Go through the west exit and open the chest to get the Map. Kill all the Stalfos to make the door open.
Reach the Mini-Boss a Fourth Time
Go back the way that you came. In the room with the button and the five blocks in the middle, if you arrived from the north, push the middle block down, then go west, and go back east and push the block to the right, then go south. Otherwise, just push the middle block to the right and go south.
Go west to return to the room where you first fought Master Stalfos, then go south to the northern crystal room. Go south again to the southern crystal room, then go south once more to a room with four statues in the middle. Kill the Keese and Helmasaur here, then go west. You should be back in the room where you got the Compass. Go down the stairs in this room.
Jump across the chain platforms the way that you did before. Afterward, you will be in a room full of crystals. Kill the Stalfos to open the door, then go through.
Master Stalfos 4
Fight Master Stalfos the way that you did before. This time, instead of running away, he stays and you can defeat him.
Get the Hookshot
After Master Stalfos is gone, you get the treasure that he stole: the Hookshot! You can use it to latch onto distant objects and pull yourself across.
Get 200 Rupees
Go back the way you came until you are in the room with the four statues that have Keese on them. You can go northeast from this room and use the Hookshot to reach the chest across the gap. It contains 200 rupees.
Get a Second Key
Go back to the room with the four statues with Keese on them. Go north to the crystal room, then go west. Kill the Helmasaurs (you can use the Hookshot on them to pull their masks off), then go north.
Get the arrows if you wish, then go west. Use the Hookshot to go to the left side of the room, then go west again.
Use the Hookshot on the chest to go across. Open the chest to get a key. Use the Hookshot on the Helmasaurs, then go east.
Get the Nightmare's Key
Go back the way you came until you are in the southern crystal room. Go north to the northern crystal room, then kill the monsters and go north. You will be back in the room where you first fought Master Stalfos. Go east.
Go north to the room with the switch and the five blocks in the middle. Push the middle block up, then go west to a room with some crystals that can be broken with the Pegasus Boots. Go north.
In this watery room, there is shallow water, then an area of deeper water. Swim into the deep water and go to the middle, then dive. You will enter an underground passage.
Swim through the passage and go west. Go up the ladder at the other side.
Use the Hookshot on the hook across the gap. You will pull the bridge out. Walk across it and open the chest to get the Nightmare's Key.
Get a Third Key
Go back the way you came until you are in the room with the area of deep water that you dived into. Go south from there to the room with crystals and Traps, then go east from there to the room with the button and five blocks in the middle. Push the middle block to the right, then go north.
Jump over the gap, then jump diagonally to the tile in the southeast corner of the room. Use the Hookshot on the chest up above to go across to it. Open it to get 50 Rupees. Then go east to the next room. Use the Hookshot on the blocks across the gap, then open the chest to get a key.
Reach Another Mini-Boss
Go west, then go north. Use the Hookshot on the bridge to pull it to you, then go up and open the chest to get 50 rupees. From there, use the Hookshot on the northwest block to go across.
Go south until you reach the room with the five blocks in the middle again. Push the middle one south, then go west, then east again, and push the block to the right so you can exit to the south.
In the next room, go west to where you first fought Master Stalfos, then go south to the northern crystal room. Go south to the southern crystal room, then go west. Kill the Helmasaurs, then go north.
Use the Hookshot to extend the bridge. Lift the pot to find a fairy. Then go north.
Unlock the key block, then go west.
The Gohmas walk from side to side. If you get near one, it will eventually either shake and run toward you, or it will stop completely and then open its eye after a moment, shooting a fireball at you. If it shakes, wait for it to start moving toward you, then run away. If you start running away as soon as it shakes, it will come directly to where you are running. If you have the Bow and Arrow, which you can buy in the village shop, it makes this battle easier. Just shoot Gohma in the eye. Otherwise, just use the Hookshot on their eyes.
Reach the Nightmare
Use the northeast door to leave the Gohmas' room. Go down the stairs. In the underground area, go to the left to reach the next room, then use your Hookshot on the statue to go to the upper part of the area. Go up the ladder at the end.
Open the key block, then go north. Use the Hookshot on a block across the way. Go west again. Open the Nightmare's Door and go through.
The eel will swing its tail from the center of the room. It keeps going in the same direction, so keep going in a circle around the room to avoid the tail. When the eel's face appears in the wall across from you, pull it out with the Hookshot, then hit the heart in its body. You need to pull the eel far out of the wall to make its heart visible, so don't pull the eel out unless it is far away. You might be able to hit the heart multiple times before the eel goes back into the wall. Be careful, because sometimes the eel in the wall is fake and will slither around the room before exploding. Sometimes after hitting the heart, the spinning tail starts going in the other direction.
When the eel is defeated, it leaves behind a Heart Container.
Get the Musical Instrument
Go north to get the Wind Marimba. You get a hint to go to the shrine next. This is referring to the Face Shrine, which is north of the Animal Village.