Morpha

Giant Aquatic Amoeba: Morpha (水棲核細胞モーファ, Aquatic Cell Nucleus: Mōfa) is the Boss of the Water Temple in Ocarina of Time. Probably created by Ganondorf once he acquired the power of the Triforce, it has complete control over the water in the room in which it resides, moving swiftly through it and creating long water "limbs". This monster is responsible for the state of Lake Hylia as well as the frozen condition of Zora's Domain.

This creature may seem to be a fearsome tentacle made of water, but in all actually it is only a bouncing red ball. This ball is Morpha itself. The advantage it has is that it can manipulate the water in any way it likes, creating one (and eventually two) large water tentacles. These tentacles try to grab Link, squeeze him, and toss him toward the spikes surrounding the arena.

When Morpha is defeated, the core will burst in a spray of water. The tentacle will cling to life as long as it can, using up all the water in the central pool. Once it uses up all the water, it will drop to the floor and splatter.

Link's rewards for this victory is a Heart Container and the Water Medallion.

Trivia

 * Din's Fire is capable of evaporating Morpha's tentacles.
 * Morpheel is a reference to Morpha, both in the way its first stage is defeated and in name.
 * Morpha can be very easily defeated if you use the Longshot to pull it, and then keep doing it while approaching the corners of the room to avoid it escaping.
 * After Morpha is defeated, Lake Hylia is restored. However, Zora's Domain remains frozen.