After freeing the Spirit of Power, you need to return to the Temple of the Ocean King to find more clues.
About the Temple
BEWARE! If you get a Game Over in the temple, you will have to do everything over again!
Go down to the area below, then go north through the door under the altar. When you go north in the next room, Leaf explains that the time remaining in the hourglass is shown in the upper-left corner of the screen.
When you are standing on safe tiles, the hourglass will not be drained.
Go north and tap the stone door to open it. Go north to go down the stairs.
Temple of the Ocean King B1
When you arrive in this area and go south, two Phantoms will appear. You can't defeat them, so you have to avoid letting them see you. The yellow cone shows which way they can see.
Go east and you can talk to the skeleton to find out that you have to light the two torches. Go to the northeast corner of this floor and hit the crystal switch there. One of the torches will light up, but it will only stay lit for a limited amount of time, so be quick. Go to the southern safe zone, and when the Phantom is walking away, go to the left and make the boomerang go to the torch on the right, then the torch on the left. If you don't make it in time, just go back to the northeast and hit the crystal switch to try again. If you do it correctly, the flames will disappear from the southwest of the area.
Go to the southwest safe zone and wait for the Phantom to go north, then go up to the safe zone on the left. Then when the Phantom is walking south, go north, then east. Talk to the skeleton to learn about the red pots. Hit the pots to create small safe zones, then go east and step on the switch to open the northwest door.
When the Phantom is walking south, go to the northwest and get the key that was behind the door. Then make your way to the northeast area of this floor, and use the key on the locked door. Go down the stairs.
Temple of the Ocean King B2
You need to lure the nearby Phantom away from the wall so you can pull the lever behind it. One way to do it is to hit a crystal switch. The Phantom will hear it and come down to investigate.
After you pull the lever behind the Phantom, the nearby flames will disappear.
However, you need to hit the two crystal switches (one is to the left of the Phantom, and the other is southeast of that Phantom) to make a key appear in another part of the room. Stand southwest of the Phantom and use the boomerang to hit the two switches. Each switch only stays on for a limited time, so try to hit both switches with one throw of the boomerang.
After that, go southwest past where the flames were before you pulled the lever behind the Phantom. Then go west from there and break the red pot and stand in the small safe zone.
Use the boomerang to hit the crystal switch just below the flame barrier. Then you can go south and stand in the safe zone. Go east when you can, and you can go north past the blue tiles and talk to the skeleton. To the east, there is a crystal switch, but don't hit it yet. Instead, wait for the Phantom to go west, then go east and you can hit a red pot to make a safe zone. Then go north from there. Step on the switch. The spikes will come back up if you are not standing on the switch, so stay on the switch and use the boomerang to get the key.
Now go back to the blue tiles and go north, then east, and hit the switch to lower the red blocks. Go northwest and use the key on the locked door. Then go down the stairs.
Temple of the Ocean King B3
Go to the southwest corner and pull the lever. This will get rid of the flames blocking a platform in the southeast. Go to that platform and break the red pot to make a safe zone. The two switches here make a trap door open down below. Open a trap door when the Phantom is walking there.
Then go up and wait for the spikes to go down so you can get the key.
Then go to the southeast corner of the room and open the chest to get a Force Gem. A cut scene will show you the pedestals where you need to take the Force Gems.
Carefully carry this Force Gem west, then north, then east to the pedestals (if you try to go past the spikes while holding the Force Gem, you will move too slowly to avoid the spikes). Tap a pedestal while holding a Force Gem, and it will go onto the pedestal.
There is another Force Gem behind the locked door in the southwest area. Unlock that door and get the Force Gem, then take it to the pedestal.
Then go to the northwest corner of the area and open the chest there to get the final Force Gem. Take it to the pedestal.
After you have thrown all three Force Gems onto the pedestals, the door will open. Go through.
In the next room, there is a door to the north, but it won't open for you right now.
Go west and Ciela will notice that the hourglass has stopped. This room is safe. Go to the northwest corner and open the chest to get the Northwestern Sea Chart. A blue warp point will appear to the right. Step on it to go back to the first room of the temple.