All you need is the fairy bow, arrows, an ocarina, iron and kokiri boots, Zora Tunic. Enter the Water Temple as normal. You should find yourself in the big main room of Water Temple(the one with the tower in the center, you know which one I'm referring to). I'll call this room the lobby. Equip your iron boots and sink to the lobby floor. Find the room with Ruto, as you would normally, and listen to her yammering. When she swims up, follow, as always, get the goods from the room at top, then go to the Triforce engraving and lower the water. You know how. Anyhoo, jump down, use your bow to gain entry to the barred room there, and find the prize within. There, you should have at least one key now, I don't remember exactly, but it is unimportant as far as this all is concerned. Now enter the lobby, and go right up to the tower, on the side with the door. See that locked and chained door, right there in front of you? Wouldn't it be nice to use a key on that door and go inside? Well, not really. DON'T USE A KEY ON THIS DOOR. Instead, use your Ocarina and play the Seranade of Water to warp out of the Temple, then reenter the Water Temple as fast as your little legs'll allow. The entryway is still all wet, but climb up on the ledge directly ahead and you'll see that the water level is still down all the way in the lobby. You'll want to jump off the ledge you're on, and here's how: see the ledges around the center tower? There's a gap in them directly in front of you, where the block can float up. Hint- don't jump into this gap. Aim yourself toward the left of it, and make a great leap. You'll miss the highest ledge, but where you wanna land is the ledge below it. If you made it, yay, if you didn't, try again, it's not really hard. Well, now you're on the second ledge, and it is a simple matter now to get inside the tower, as you can light the door-opening torch via lit torch, bow, and arrow. Voila! You're inside the center tower! You can be a dull gus and head straight for the water-raising triforce engraving, or you can jump down and examine the locked door that you skipped using the key on. Funny, huh? You can see the lock on the front side of the door facing away from the door and walking backward in Z-target mode. Strange, no chain or anything on the back. Of course, Navi insists that it is still locked, in that irritating voice of hers. If only there was a way to skip getting Navi... Well there ya have it. You can skip getting a key elsewhere that's a pain to get or else have an extra in the end. Whatever you like.