I have moved your question to the semi-right topic. We are still working on a Help game section. But I'll answer your question.
Most information has been copied from Devin Morgan's walkthroughs.
From the start, defeat all the enemies in the room, and then shoot the switch
on the ceiling to open the door. Then, go right through the next room and
enter the following room. (Don't worry, you'll come back to it later.) Talk
to Princess Ruto and she'll walk away from you and fall into a hole in the
floor. I know she's kinda mean but go save her by jumping into the SAME hole after her and you'll land in the basement. Talk to her again and she'll finally let you carry her around. Go
through the door behind you and go down the hallway while avoiding the
floating bubbles. In the next room, drop into the middle area and throw Ruto
onto the platform at the other side of the room. Then, press the switch to
make the water rise, and swim up to reach the other side, too. Run through
the next hallway, still avoiding the bubbles, and when you reach the door,
turn around and shoot the switch in the ceiling to open it.
Enter the next room and dodge the enemy's attacks while waiting for the
floating platform to come down to the basement. When it comes, jump on and
ride up to the first floor again where you were before. Walk along the ledge
and enter the next room with the holes in the floor. This time, make your way
to the other end of the room and enter the door to the next area. When the
path splits, take the far right path and step on the switch. If the door
shuts again if you get off the switch, place Ruto on the switch to keep it
open for you. (This goes for all the switches in this area.) Defeat ALL the
enemies in this room to get the Boomerang!
Leave the room and take the left into the room with the holes. Get Ruto and
head back to the room you were in. Go left when the path splits, then drop
Ruto on the switch you see, and enter that room. Defeat the Red Parasitic
Tentacle by aiming and throwing your Boomerang at its narrow weak spot a few
times. After you beat it, open the chest that appears to get the Map. Leave
this room and take the next path over to the left into another room. Destroy
all the bubbles in 40 seconds to get the Compass.
Leave that room and head to the right side of the room (consult the Map if
you need help). Go into the northeast room and you'll find another Parasitic
Tentacle here. Kill it like the other one, then exit this room. Now, take the
middle path into the now-unblocked chamber. Defeat the Green Parasite
Tentacle swinging from the ceiling. After you defeat it, the big barrier in
the room with the holes will disappear. Go back to the room with the holes,
get Ruto, then drop into the new hole. You'll drop onto a ledge in the
basement, which you couldn't reach otherwise. Enter the door there and when
she asks you to, throw Ruto onto the platform so she can get the jewel there.
The platform will take her up a couple floors and bring a giant octopus down
to attack!
Defeat it by running around and around until you finally get behind it. Then,
use the Boomerang and attack the weak spot with the sword. Repeat the process
a few more times to defeat it, then climb onto the platform to get to the
second floor. Go down the hallway and enter the next room. Use the Boomerang
to make the shaky blocks stay still for a while, then jump across them to the
other side! In the next room, jump onto the ledge and ride it down to the
first floor again in that room you skipped earlier. This time, you're now
able to reach the switch there. Get a crate from the nearby ledge and put it
on the switch to keep the door open for you.
Enter the next room and climb up the vines on the wall in back of the room.
Stand a little bit back from the glass panel and use Z-Targeting to aim at
the switch at the other side. Once your aim is set, throw the Boomerang so it
swings around the glass and hits the switch! Now, get back down to the ground
and enter the now opened door. Go down the hall and enter the next door to
reach the boss, Barinade! Defeat him and make sure to Take the Heart Container after you beat it and leave Jabu-Jabu's stomach.