Ocean King and back
You should have around 20 minutes of hourglass time at this point. Use it to dive deeper in the Ocean King temple. Using your bombchus and grappling hook, you should have no trouble making it back to the bottom and claiming the Northeastern Sea Chart (check the video at the "Final trip" tab for more). Actually, we did this part before the Temple of Ice, but it might make more sense to do it after.
Northeastern Sea
Back in the NE sea, you should come across another Traveler's Ship. Beat the enemies inside and meet the smiling guy, who'll offer you a mysterious present or normal present. Take the normal (treasure map) and he'll give you the mysterious too (some "hero's clothes"). Then proceed to the Isle of the Dead in the upper ride hand corner.
Up first is the cave filled with books. Read them all and then start bombing the hallway to the left. You'll find a hole that leads to ship parts and a Courage Gem. Back outside, you'll head towards the northeastern temple - not much in here except a tablet that tells you something about 13 steps and 7 steps. It's trying to direct you to a hole outside. Want better directions? Find the tall pillar with the switch on it, place Link in front of it (where you can fully see Link) and walk three down and one right. It's basically an "L" block from Tetris. Down below, bomb the wall and gather the goods. Continue on until you're back outside, hit the switch and head to the sage's graveyard.
Follow the tombstone's directions (N-E-E-N-N) through the pyramid temple and you'll get a new necklace, one that'll let you pass the cyclone guarding the other island. You can discover Maze Island if you like, but its treasure hunting minigame will chew up a lot of time.
Isle of Ruins
This dizzying island is packed with obnoxious fetch quests and a trap-laden temple. Ugh. First use the narrow walkways in the southwest to get at the western pyramid (make note of all the tablets you see too). A new path will open. Move east to the other temple. You'll receive the King's Key. Take the key back to the first temple and the water level will lower across the island. Hop down into the drained area and head east. The center area requires you to push boulders down stairs to clear the way, but one boulder actually serves two purposes. One is to the south, where it'll clear your path, but leave and re-enter the area to push the same rock east and reveal the way to a Wisdom Gem. Hit the switch near the southern pyramid to connect this area with the mainland.
Another knight, another test. This one wants you to run through the now-drained labyrinth from earlier. Read all the tablets and you'll end up with a design for the pyramid's door. It's basically a "W" with a line across the top, but you have to draw the top line first, left to right. Then down the right side, and then back to the starting point. Kind of like a really angular Pac-Man. There's also a Courage Gem in the upper right hand corner of the maze.
Draw the design on the door and head into Mutoh's Temple.
