There are 2 downers,it's a one time thing and you have to use magic. Ok, first, go to Lake Hylia or another water source where there is a slope. Next, put on the iron boots. You then charge your sword so that it turns "fire-engulfed" and walk slowly down the slope into the water. If you "drop" down a level, your sword won't be charged anymore and you'll have to start over. If you did it right, you'll have a charged sword, and you can release it on any enemy you encounter. If your hookshot or longshot is equiped, then it will light up, while the other c-button items are faded, proving that you're underwater.