Swim following the stream and you will meet a water creature that probably saw Zelda. Follow it, then when it's behind a fence, talk to it to learn that you have to perform a spin maneuver. Talk to another creature, a bit behind you, that will teach you how to perform a spin maneuver. Get back to the first creature and perform a spin (by shaking your Nunchuck) to break the fence. It will then tell you that the Water Dragon has been attacked by a weird guy and some monsters, and that she got hurt. Follow the creature which will lead you to her, but some boulders are blocking the way. Swim to the right, aim at a Froak and perform a spin maneuver to make it explode in front of the boulders, which will then explode as well! Go ahead, speak with the creature and ask it about the Water Dragon so it shows you the right way to go. Then, swim north, aim at a Froak and perform a spin to explode the boulders here.
Keep on following your guide, then when it's behind some bars, talk to another creature next to you, which will teach you how to perform a "spin jump". Take a few steps back, swim towards the bars while underwater and perform a spin jump to get over the bars in a stylish fashion! Go north and perform a spin jump (towards the heart) to get past the obstacle. Go right on the ground, get rid of the blue Chuchus, then go right on the pier and perform a Skyward Strike in front of the Goddess Cube. Get back to the heart flower and take a look at the Bird Statue a little further. Go up the path and open the chest to find a Goddess Plume, then jump into the water and keep following it.
Here is a big fish! Get close a little bit, it will dash at you and get stunned on a wall. Quickly perform a spin maneuver to get rid of it. Keep on following your guide up to a door that it opens with its "head", swim a little more and surface.
Speak to lady Water Dragon who is called Faron and tell her that you came for the flame. She tells you about Ghirahim who attacked her, that the water of the basin is sacred and that she needs fresher and stronger water. Accept her request to get some sacred water to heal her and Fi adds that you can now dowse it. Swim towards northwest, get out of the water and follow the passage leading outside.
Take a look at the Bird Statue on the right, then follow the path. Push the log to create a shortcut and jump. Fight or avoid the enemy with a huge belly and shield (Moblin), then go left, jump on the log on the right and jump higher. Head north to the Viewing platform, grab the vine and go into the Deep Woods. Go to the tree, climb on the log and jump higher (if you haven't pushed it previously, you have to go through the ropes again), go ahead north, climb on the log to the left, then get in the...
After Fi confirmed that sacred water lies in the depths of the temple, go down the stairs until a Mogma appears to tell you about treasures. Keep on going down the stairs and open the next two doors. Go straight ahead, strike the Bokoblin, but the door is locked again! Go left, open the door, and you will meet a Mogma who admits to have stolen the key and buried it somewhere. Get out and open the door in front of you. Jump into the water, swim towards the bottom to the left and get in the small passage. Surface, climb the vines, go ahead and dig at the cross' spot to get a Small Key! Crawl into the tunnel, then leave the room, go right and unlock the door.
Go to the back, but two Bokoblins are shooting arrows at you! Send your Beetle on the hanging bomb and drop it on them. Go across using the rope, then open the big door. Three Stalfos are there to welcome you! Attack them using your Shield Bash attack when they are about to hit you, but also by dropping some bombs on the ground and drawing them to your traps so they get stunned for a few seconds and you can hit them. Don't hesitate to break pots to refill your bombs and hearts. After defeating them, open the next door, then go left, under the waterfall designated by the Dowse function and pick up some Sacred Water in an empty bottle.
Back to the entrance of the temple, get back into the Faron Woods, then head south, then towards the Floria Waterfall and get into the Dragon's Chamber. Talk to Faron's spirit, who sees the sacred water you brought back. After pouring the precious liquid into the basin, the dragon turns into her real form! Outside, the Water Dragon will part the waterfall's stream and uncover the way to get the flame! Go ahead, jump into the water and perform a spin jump to get into the...