Tailpasaran
The Tailpasaran, like most of the enemies found in Jabu-Jabu's Belly, is electrified, so don't even try to hurt it with your sword. The best thing to do is to wait until it emerges from the ground, Z-Target it and throw your boomerang at it to destroy it. If you don't have the boomerang, however, quickly run from it before it comes out.