Head through the door to the west to proceed inside the Sandship. A lock blocks the door nearby, and a set of stairs on your right leads down to the floor below, where you'll see a small corridor across a pit of sinksand. Keep winding your way down to the bottom of the ship, passing right by the massive boss door, and you'll see a room littered with sand. Blow the sand away with your Gust Bellows and examine the symbols on the floor. They indicate the directions you need to strike the directional block to unseal it. For the untrained eye, the order you'll need to strike the lock is from below, from above, below again, and finally from the right.
Execute this order to open the lock. Inside the next room you'll find a Small Key, which you'll need to take back to deck level and enter the locked door. Beyond the door you'll find the ship's mast, where the leader of the pirates, Scervo, awaits. Fight him off with a combination of jabs and Shield Bashes to knock him back along the narrow arena. After about three or so rounds of sparring, he'll topple from the ship and a chest containing the Bow will appear.
Scervo is a robotic pirate that guards the Sandship, which his crew stole off the Skipper. It fights with an electrically-charged sword, kind of like the Technoblins. One has to wonder whether the Technoblins stole their technology from the robotic guardians of this region...
Link's always had a bow and arrows as part of his inventory, but now they're stronger than ever. Pick off enemies from a distance, and if you're good enough you can even take them out from much closer...
2 - Climb the ship's masts and activate the Timeshift Stone.
Fi will point out a new type of switch on the deck that you can strike with your Bow, so head back there and activate it. This will cause a Timeshift Stone to appear which you can hit from afar with another arrow. A group of Bokoblins will pop up as you get dragged into the past, and one of them will seal off the crystal. You can't have this, so pick off the Bokoblins with your Bow and scan the masts for another blue target you can strike with an arrow. It'll activate one of the ziplines, which you can use to ascend on top of the sails.
The ziplines are staggered, so whip around to face the opposite direction and look for another arrow target to activate the next one. At the next mast, take out the Bokoblins and stick your sword into the conduit here. Give it a good 90 degree twist to unbar the Timeshift Stone. Now you can manipulate it again to get further in the Sandship.
3 - Reactivate the engine room generators.
Hop back down to deck level and look to the northeast corner of the main deck. You'll see a life raft which you can lower by shooting the arrow target situated above it. Once it's lowered, head back into the ship through the west door you used earlier. In the room where you used to find a sinksand pit, head into the second opening on the left and look up through the grate in the ceiling. You've got a pretty good view of the Timeshift Stone. Shoot it to bring down the electrical barrier here and grab the Dungeon Map from the next room.
Don't restore the ship's operations just yet. Head across the sinksand and make note of the fan on the wall to the right as you head down the corridor. Since the ship's deactivated now, shoot an arrow through the dormant fan at the arrow switch on the other side to open the adjacent door. Inside, fight off the Thunder Keese and then move the block out of the way of the fan between the two rooms. Step on the pressure switch to open a sliding panel in the opposite room. Again, it's fortunate that the ship is inactive, because you can fire an arrow through the fan and hit the arrow switch the panel reveals.
This will open the door to the opposite room. If you strike the Timeshift Stone again, you can head inside and twist the power node here to activate one of the ship's two engine room generators.
Take a peek in the second door on the left in this same corridor. Push the block nearby onto the pressure switch to open panels that lead to the outside of the ship. Lowering the liferaft earlier will let you step out one of these panels right onto it, at which point you can raise it again with another arrow to the switch and then hit the Timeshift Stone from here. Lower yourself back down and climb back inside the ship. The electrical barrier has subsided, and you can pass through to the second generator room. Fire an arrow through the grating in the ceiling to reactivate the ship so you can power on the generator, then head back out into the hall.
4 - Rescue the captured robot crew from the brig.
With both generators active, you can now rescue the robot sailor crew from the brig, where they're being held captive. Climb down the ladder attached to the left opening in the room you used to access the liferaft and head into the opening. Follow the corridors to a door that will lead you to the engine room, just beneath the brig. A series of pistons up ahead will crush you if you're not careful, so time your movements to make it through. Ascend the ladder at the end of his first stretch and look to the Whip target to your left. You can swing across the gap and continue around the engine room, but you can also swing into the alcove to the right to claim some Rupees and Treasures.
The next set of pistons move in tandem with one another. You'll have to dash beneath them all in a row to get past. Climb the ladder ahead and instead of trying to run underneath the next set of pistons, use the Whip to swing on top of them. Jump from the first piston to the next, then climb up to the ledge and pull the lever to create a shortcut. The crawlspace next to the lever leads to a ladder that will carry you to a second lever that will open the barrier sealing off the brig. One of the robots who was formerly trapped here will give you a Small Key as thanks for freeing him and his crew.
5 - Recover the Squid Carving and enter the ship's deepest chamber.
Take this Small Key back up to the deck, climb up the ladders on the east side of the ship, then hit the Timeshift Stone to restore the time period to normal. The Small Key can easily open the locked door here. At the bottom of the stairs, head through the open doorway at the far end of the room, stand in the sunlight, and point your Bow up at the Timeshift Stone. Activating it will call some enemies forth, but it'll also allow you to stand on the pressure switch nearby and shoot an arrow through the now-open panel at the arrow switch across the way.
Pass through the door into the next room and claim the Squid Carving from the big chest. Take this Squid Carving back to the massive boss door at the opposite end of the ship and insert it into the lock to reach the heart of the ship.
6 - Escape the Sandship and defeat Tentalus.
The ship's under attack! Giant tentacles are tearing through her hull. You can chop through them with a Skyward Strike, so do so and clear a path as you make your way back to the deck. Once you've exited the ship, you'll begin your battle with the giant squid fiend, Tentalus.
Abyssal Fiend Tentalus
Tentalus is trying to tear the Sandship apart with its gargantuan tentacles. You'll have to cut into a few of them at first before the monster will truly reveal itself, but only a Skyward Strike will do the trick.
Tentalus will start by ripping through the ship with massive vertical tentacle thrusts. Once again, chop through them with a Skyward Strike to sever them. A few tentacles down and Tentalus will rise from the deeps. Its single eye is its weak point, so charge an arrow and fire away to stun it. Then rush towards its eye and deliver rapid blows with your sword.
The tentacles will try to grab you, so try to keep moving, even as you charge your sword. If one happens to snag you, shake the Wii Remote and Nunchuk violently to break free. Once you deal enough damage to the central eye, Tentalus will start breaking the ship apart and barrels will roll towards you from the deck above. That's your cue to use the block against the upper deck as a stepping stone to climb higher.
During this last phase, keep shooting Tentalus in the eye whenever possible to stun it, but watch out for the snapping tentacles. You can cut through them with your sword, but they come at you from all sides so it can be hard to hit them all. A few more rounds and Tentalus will fall.
Claim the Heart Container it leaves behind and activate the Goddess Crest with a Skyward Strike to receive the blessing of Nayru's Flame. Your Goddess Longsword will transform into the Goddess White Sword, giving you the ability to select four additional Dowsing targets at once!
Goddess White Sword
Thanks to the power of Nayru, your sword can now hunt down more objects with its Dowsing capabilities. You'll need this ability in the coming trials.