Jabu Jabu's Belly
Use a fish to open, Jabu's mouth. When inside use your slingshot to hit the switch on the ceiling. Go through the now unlocked door. Keep on going and go through the next door. Inside the next room you'll met Princess Ruto. Drop down the same hole that she fell down. Talk to her again, picker up, and go through the door that's behind you. Walk on until you find a gully that has a floor switch in it. Drop down into the gully and throw Princess Ruto up on the other ledge, then press the floor switch. Climb up on the ledge with the Princess and then pick her back up and go on down the corridor. Drop her and use your slingshot to hit the ceiling switch. Go through the door. Drop Ruto and take out your shield to defend yourself against the Octorok. Then climb onto the moving platform. Once back up to the top, jump onto the platform and go towards the room where you first met Ruto. Go straight across this room to the other door on the other side. Go through it. Go to the east and step on the floor switch. Take her inside the room with you. Here you'll have to destroy 4 Stingers. After you destroy them you'll receive the boomerang. Pick up the Princess, go back out the door and go towards the opposite room. Then step on the floor switch and leave Princess Ruto on top of it. Then go in the room. Destroy the big Tentacle that is hanging down from the ceiling. You should receive the Dungeon Map after you destroy it. Go back out the room and pick up the princess and turn left and go down that corridor to the next room. Here you'll have to destroy bubbles. After you destroy them all you'll receive the the Dungeon Compass. Then exit and go to the other side of this room. Go towards the other floor switch that required both of your weights, but turn left and go down that corridor and go into that room. Here you'll have to destroy another Tentacle. After you destroy it, the central door is now open for you to enter through it. Go there and drop Ruto inside. Here you'll have to defeat some jellyfishes and the Green Tentacle. After you defeat it, go back to the main room where you met Ruto, drop down the now open hole. It did have a green slimy tail over top of it. Once down there, kill the two skulltulas and get the tokens with the boomerang. Turn around and go down the small corridor and go through the door. Then throw Ruto onto the platform. Kill the Bigocto that drops down from the platform and then get on the platform. Go through the door on down the corridor. Kill the Octorok and hit each of the red swinging platforms with your boomerang. They should be stunned. Now jump from one to another and go through the door. Jump on the platform Then, grab one f the boxes and take it back over towards the door with the floor switch in front of it. Press the floor switch and put the box over top of it. Kill all the Biri and climb up the rough vines. On the opposite side of the wall there is a Skulltula. Climb up the vines and use your boomerang to hit the ceiling switch. Jump down off the vines and go through the door.
Boss: Barinade
The best way to defeat it is to first Z target the stem looking things that are attached to the ceiling. Hit them with your boomerang. Then hit all the jelly fish looking things and destroy all of them. Once there are no more of them, keep stunning the middle part and strike it with your sword.