This part will take you through your first visit to the Temple of the Ocean King.
Path to the Temple
Now that we're on the path heading for the Temple, go north and then to the left, slaying Red Chuchus that are in the way. Then climb up the stairs, and we should be near the tree that we marked out on the map earlier. Do a somersault roll into the tree, and it will give you a green rupee worth 100 rupees. Great!
Now continue heading to the left and then down, noting that there are two blocks at the top of a staircase. We can't get rid of these blocks yet, so don't worry about them. Continue to the left, and soon we'll see a crack in the rock wall that we can't do anything about yet. Just mark it on your map for later and continue to the left and then go north. At the top of the stairs is the entrance to the Temple of the Ocean King. Ciela will make a comment about the Temple ruining those who enter into it as we take our first gaze at it. Still, we need to find Linebeck, so let's enter.
Inside the Temple
In the first room that we enter, we see an hourglass sitting on a pedestal overhead at the top of two sets of staircases, and there are also skeletons of people unfortunate enough to enter this Temple littering the floor. You can listen to the skeletons speaking their regrets, but mostly we just want to go inside to the first floor.
As we enter the floor, we hear a voice crying out, coming from a room just up ahead to the north. The person crying out is Linebeck, the ship captain we're looking for, who is trapped in a room with spikes barring both doors. He'll say that he would ordinarily get himself out, but he sprained his ankle, and now he needs our help. Agree to help, and he'll say there must be a way to disarm the spikes. However, the instant we start to go north, Linebeck will warn us that this Temple will "suck the life out of you", and that as long as you're standing in special areas marked with purple tiles on the map (what we call Safe Zones), you'll be safe.
So now let's get to finding a way to disarm the spikes. As soon as we step outside the first Safe Zone that we were in, you'll notice that Link's heart meter will take one-quarter heart damage every few seconds. Head first for the Safe Zone that's near us on the left, then head for the one northeast of our location where a locked door is. Hit the switch orb that's in that Safe Zone, and this will disarm the spikes around Linebeck's Safe Zone, encouraging him to make a quick bolt across to the one near the entrance. Now head for the Safe Zone that's to the right of us, and you'll see a treasure chest that contains...nothing? Ciela will wonder if somebody took what was in it before us. No matter, we need to get back toward the Safe Zone near the entrance. Zip across to the Safe Zone that's southeast of our location, breaking a pot or two to restore our health, and then join Linebeck where he is now.
We'll enter a cutscene where Linebeck explains his situation and wonders what we're doing in the Temple looking for him before he roughly shakes Link up, believing he's after the treasure on board the Ghost Ship. Ciela defends Link by saying that he's after saving his friend. Linebeck will then say that he will help, but he's also looking for information on the Ghost Ship, and he would have gotten hands on it if he hadn't "sprained his ankle", which Ciela quickly denies. Linebeck roughs up Link again, telling him to go find that information on the Ghost Ship, and he will give us the small key to open the locked door...as Link gets up rather dazed!
So now let's go back to the Safe Zone where we found the locked door, noting that we can now go through the Safe Zone that we disarmed the spikes from. Open it and go through until we reach the Safe Zone to the northwest of our location. Hit the switch orb in that location, and we'll see some spikes nearby being disabled. Now quickly go across to the right and up to the Safe Zone in the northeast corner of this floor, watching out for both the spikes popping up going one way and a trap door opening going the other way. Then hit the switch orb located there. If done quickly enough, you'll disable the other spikes and cause a door at the north end of the floor to open. Go replenish your hearts and then enter through that door into a room where we see a treasure chest. It will contain a Sea Chart that will unlock the area of the Southwestern Sea. Now we can take it to Linebeck.
Return back to the Safe Zone that you were in with Linebeck. You'll notice that Linebeck is now gone.
Outside the Temple
Leave the Temple, and we'll find Linebeck waiting for us outside, making excuses about his leaving in a hurry while Link risked his life getting the information. Link will show him the Sea Chart we found, and Linebeck will run off with it, caring more about treasure than helping Link rescue his friend. So now we have to chase after Linebeck.
Head back through the path we've taken to get to the Temple to return to the port, and as soon as we reach the boat, Oshus is there with Linebeck, stopping him from taking off with the Sea Chart. Linebeck says he's inspected the map and it holds no secrets on it. Oshus takes a look at the map and finds something a bit flaky on one section. He gives it to Link in the hopes that he'll be able to find out. Using the stylus, rub it over the island that's on the southeastern portion of the map. We'll see a crest appearing. Oshus explains that this is the Isle of Ember, where Astrid the fortune-teller lives, and that she might be able to tell where the Ghost Ship might be. Oshus tells Ciela to go with Link for assistance and for possibly restoring her lost memories.
Though Linebeck grudgingly decides to take Link and Ciela along to the Isle of Ember, he tells Link that he'll be shark bait without a shield, so we need to go buy one. Head for the shop that's south of the Milk Bar on the southwest part of the harbor town, and the lady there will sell you a shield for 80 rupees. You should have enough to buy one at this point. After you get the shield, return to Linebeck at the boat and tell him you're ready to ship off.