Unagi

The Unagi is an enormous sea serpent capable of spewing out large water streams, like a geyser. It is unknown exactly how this creature does so; it is possible that the Unagi does this through Waterbending, much like dragons do Firebending. The only known Unagi is the one that lurks in the bay of Kyoshi Island and is a powerful carnivore that will prey on almost any animal in the water but feeds almost exclusively on the Elephant Koi which also inhabit the bay of Kyoshi Island. The Unagi is seen in "The Warriors of Kyoshi" and mentioned by Suki and Sokka in "The Serpent's Pass".

Anatomy
The giant's body seems to be several hundred feet in length. It has smooth, dark brown skin, without any scales. Sharp spikes line the back of its body from head to tail. The Unagi has bright green eyes and a mouth full of sharp, interlocking teeth. A large fin protrudes from the top of its head and appears to be made of approximately seven hollow bone-like structures with connective webbing. The Unagi can expand and contract this fin. Below that, on either side of its head, are four bright yellow stripes, possibly its gills. Unagis have two very long barbels and glands that it uses to blast water at its prey. They also have tendrils for its prey to swing on, 16 pairs of teeth, and an instinctive fear of anything bigger than them.

Connection
Unagi is the Japanese word for freshwater eels and the sushi made from them. The Unagi in the Avatar World is named for the eel and its long serpentine body is its primary connection with that animal.

Behavior
The Unagi is a very dangerous creature. Because of its vicious nature, the people of Kyoshi Island don't swim in the bay where it lives. When the Fire Nation attacked Kyoshi Island and set it on fire, Aang jumped on the Unagi. Using the barbels, Aang forced the Unagi to spit out water, putting out the fires.