Receive the Zora Scale
If you haven't gotten the Zora Scale yet, then after getting the essence from Jabu-Jabu's Belly, go south until a Zora comes up to you. You will receive the Zora Scale, which allows you to enter the Sea of Storms.
Enter the Sea of Storms
The Sea of Storms is in the past. If you are playing a Linked Game, you can access it in the present, and you can access a soft soil location in the south part of the Sea of Storms in the present.
The Sea of Storms is at the bottom of the map, in the center. Dive underwater and talk to the Zora. The Zora will see the Zora Scale and allow you to go to the Sea of Storms. Swim past where the Zora was, then go to the surface.
Find the Pirate Ship
Swim around the Sea of Storms until you find the pirate ship (it will be there in the Present in a Linked Game). Swim up to it. Talk to the captain and give him the Zora Scale. He will give you the Tokay Eyeball.
Get a Ring
Before leaving the Sea of Storms, dive underwater and swim to the cave on the right side to find a ring.
Put the Tokay Eyeball into the Statue on Crescent Island
Go to Crescent Island in the past and find the statue that has only one eye. Check on the missing eye to put the Tokay Eyeball in place.
Go through the Cave
In the cave, kill all of the Gibdos to open the door. Go through.
Get rid of the pot and jump over the spot next to the spinning blade trap. Go down and bomb the rock out of the way. Trigger the blade trap, then walk past when it's returning to its spot. Push the pot up and quickly hit the hardhat beetles out of the way. You can also get rid of them by shooting them with Gale Seeds.
In the next room, use the Cane of Somaria to push a block around the invisible path. Start by going to the bottom of the starting ledge and walking straight toward the green rock. Then go straight down to the wall. Create a block to your right and push it right until it disappears. Then go up once, then right until the block disappears, then create a block above you and push it until it disappears. Create a block to the left and push it until it disappears. Go up all the way to the wall, then jump over one square to the left to reach the stairs.
After going down the stairs, swim and jump to the ladder on the far right. Climb up.
Outside, go to the surface of the water and push the rightmost statue to the left.
Sea of No Return
Go north from the entrance to see a cliff in front of you. Exit northwest. The red centaur-like enemies are Lynels. They can shoot sword beams at you. Follow the path around. When you see the dungeon entrance, exit east and then continue to follow the path to the Ancient Tomb.