I am not the stuff of walkthroughs, but I can provide a little cheat I discovered in order to power through Ocarina of Time Master Quest. Now I know there probably aren't many out there at this point playing the game, but just in case I felt it should be posted.
So this is how you beat the water temple without ever having to change the water levels: Once you enter the water temple equip your lead boots and sink to the very bottom of the temple. There should be two available doorways to go through. Head for the one that doesn't have the massive pit in front of it, go a little to the right and there it shall be. Once you enter Princess Ruto is there to pout about her everlasting princess love and other forced proposal things and then tell you to follow her to change the water levels. As you drift upward there are three levels. Before you reach the surface you should see a level that has a big hole in the wall. Swim toward the ledge and again equip those lead boots (as if you needed reminding). There will be a stone slate directly in front of you on the far wall. Get out your hookshot and hit the slab. A chest will appear. Now as you know, you can't open these chests underwater, at least it didn't let me when I took the normal approach. Instead of deserting my post I took the hookshot out and latched on to the chest, mashing A the instant I got close enough to it. This forces the chest to open and when successful you get an amusing distorted chest open fanfare song. You now have the longshot! You will be able to access all the other necessary rooms in order to beat the dungeon, however if you're going for 100% completion then you will miss some gold skulltulas. Otherwise, thank you lord I don't have to put up with the notorious pain that is the water temple.