The Sandship is a dungeon that protects Nayru's Flame.
Find a Goddess Wall
Start by going into the room on the west side of the deck. Save, go down the stairs, and strum the harp near the butterflies to reveal a goddess wall.
Get a Key
Go down the southern hall to find some keese and a door. Go through.
Throw a bomb at the electro spume in this room, then run across the sinking sand. Try walking in the sand for a very short distance and then run through. You will get across but run out of stamina at the very last moment.
Go down the hallway beyond the sinksand, then go around the corner and down the stairs. Go through the door.
Kill all of the arachas, then save at the bird statue up ahead. Sit on the chair for a while if you need to heal up.
When you pass the large, barricaded door, Fi will say that it leads to an important room. Across from the large door, you can see a room with several treasure chests in it. You can't access it yet, but keep it in mind for later.
Go around the corner and kill the keese that attack. These are thunder keese, so make sure not to hit them when they are sparking. Go through the door.
To unlock the door crystal, first blow the sand away from the floor and kill any arachas that pop out. You will find four symbols on the floor. Look at the symbols next to the door and you will see that they are red on top. Similarly, the symbols on the floor have a red side, which is the top. Also, each floor symbol has a different number of red spokes. The first one has one spoke, the second one has two, and so on. This way, you can figure out the puzzle.
Hit the door switch in this order: bottom, top, bottom, right. Go through and open the chest to get a key.
Reach the Mini-Boss
Go all the way back to the first bird statue that you found after going inside of the ship. There is a locked door next to it. Go through.
You have a narrow area in which to fight Scervo. Use thrusts and downward slashes and upward slashes. As you hit Scervo, you will knock him back toward the edge. Be sure to run toward him to keep him from getting too far away. You need to quickly hit him before he regains his balance. If Scervo defends himself and you can't hit him, be ready to do a shield bash if he attacks. Once you push him to the edge, he will lose one of his swords, and the barrier behind you will get closer.
If Scervo reaches back with his sword while standing on one leg and blocking with his hook, be ready to do a shield bash, because he is about to hit you with his electrified sword. After you push him back to the edge this time, he will lose his right arm, and the barrier behind you will come closer again.
If Scervo leans back, he might be about to hit you with his electrified hook, so be ready to do a shield bash. Knock him to the edge one last time to make him fall off.
Get the Bow
After you defeat Scervo, a chest will appear that contains the Bow.
Reveal the Timeshift Stone
Go back into the ship and go through the door across from you. Look up and shoot the blue target on the mast that Fi showed you a moment ago. A timeshift stone will appear at the top of the mast. Use the bow to hit it, making the whole ship go into the past.
Kill the bokoblins that appear. Go around to the back side of the mast and climb up the ladder. Kill the bokoblins up here, using the bow to get rid of all of the ones that you can't reach with your sword. Then go to the side of the mast where there is a rope going to another mast. Look across at the other end and shoot the target to make the bar come to you.
Go close to the bar and grab it when "Grab" appears on screen to go to the other side. Shoot an arrow to get rid of the bokoblin at the very top of the other mast, then use the other bar mechanism to reach the top of the other mast. Thrust the sword into the dial and turn it to the top and press it in. This reveals the timeshift stone and unlocks the door back into the ship.
Get a Piece of Heart
Skipper will arrive and ask you to rescue his crew, who are being kept in the brig. He will mark it on your map.
When you go back down to the deck, be sure to hit the target on the device that is holding a small boat over the side of the ship. This will lower the boat.
Use the bar device up here to reach the end of the ship that you couldn't climb to from below. Use the sailcloth to float down. Use the clawshot target on the far mast and make your way down to the bottom area where you will find a chest that contains a piece of heart. There is also a goddess wall here.
Get the Map
From the area where you found the piece of heart, clawshot back up and go to the main deck. Go inside of the ship and save at the bird statue. Return to the room where there was sinking sand and an electro spume in the present time. Kill the technoblins and then go into the room on the left that you couldn't get into before. Fi points out that you can see the timeshift stone through the vent. Shoot it with an arrow to get into the next room. Open the chest to get the dungeon map.
Activate the Generators
In the room where you got the map, pull down the red bar to remove the bars from this room.
Before reactivating the timeshift stone on top of the ship, run past the sinksand and go to the fan in the wall that has light shining through it into the hallway. Shoot the target on the wall past the fan to remove the bars from the door. Go in and kill the keese, then pull the block away from the inactive fan. Stand on the red switch and shoot the target through the fan. This will remove the bars from the room. Go back to the area where you got the map and hit the timeshift crystal on top of the ship. Go back to the room that you just removed the bars from, get rid of the technoblin, and thrust the sword into the dial and turn it.
Fi says to check on the crew, but you don't have to.
Go into the room across the hall. Kill the technoblins and push the block onto the red switch. If the small boat is not next to the hole in the wall on the right, you will have to go back to the outside of the ship and shoot the target on the device holding the small boat at the side of the ship. Go back to this room and go through the hole in the wall on the right to get into the small boat. Shoot the target to go up, then hit the timeshift crystal up above to deactivate it. Shoot the boat target again to go back down. Go through the door that was electrified. Kill the keese and pull down the red bar to open the door. Then hit the timeshift stone through the vent in the ceiling. Thrust your sword into the dial and turn it to activate the generator.
Get the Squid Carving
Go back out into the hallway. Go into the room next door where there are two holes in the wall that go to the outside of the ship. Go through the hole on the left and climb down the ladder to reach the engine area. Go past the pistons when they go to the top. Use the whip, but stop swinging and turn to the side to swing to the niche in the wall. Climb up the ladder here to reach the five chests that you saw before.
Go back down and use the whip to get to the other side. Run past the five pistons as soon as they rise to the top.
Go up the ladder and use the whip to get on top of the slow piston. Wait for it to rise to the top, then run forward to land on top of the fast piston. Go to the ledge at the top. Pull down the red bar, then crawl into the small hole to reach a ladder. Go up.
Pull down the red bar, then go into the brig. The robot will give you a key to the captain's cabin, and the robots will leave.
Go back to the main deck of the ship and deactivate the timeshift stone. Go into the locked door next to the two large fans. Save at the bird statue downstairs.
Go through the door into the other part of this room. Shoot the timeshift crystal through the ceiling fan. Kill the technoblin and beamos, then step on the red switch and hit the target through the gap. Before going through the door that opens, use arrows to kill any beamos that you can see through the bars. Go through and kill any remaining beamos, then go through the bars to get the Squid Carving.
Reach the Dungeon Boss
Go to the control room like Fi says. Use the squid carving to get into the room. Some tentacles will come up from the floor. Leave the room and try going down the hall. Use skyward strikes to cut the tentacles that are in the way. Avoid the rolling barrels that are coming out of the room, then go through. Go up the stairs and some water will rise. Continue on, avoiding the rolling barrels that are coming down the hall. Don't go forward too quickly, because tentacles will come out. Cut them with skyward strikes. Then go up. Fi says that the monster is on the other side of the door.
Run around the deck and use sideways skyward strikes to cut the tentacles. After cutting enough of them, Tentalus will come up. Use an arrow to shoot Tentalus in the eye, then run forward and hit Tentalus's eye with your sword repeatedly.
Tentacles will come up again, so run around and cut them with skyward strikes as before. They will come up more quickly each time, so be sure to run around constantly.
After a while, Tentalus will break some of the area that you are walking on. Run up the box that falls to go to the upper level. Use regular sword strikes to cut the snake tentacles. When you get an opening, shoot Tentalus's eye with an arrow. Run forward and hit it repeatedly with your sword. Do this again until Tentalus dies.
Get Nayru's Flame
Get the heart container, then hit the crest with a skyward strike. Fi will now be able to dowse for more objects.
Learn Din's Power
Go to the Isle of Songs and hit the crest with a skyward strike to learn Din's Power. The next trial is on Eldin Volcano.