Rooted in Polynesian mythology. They are best known as watery serpents that lived in sources of water. Considered dangerous they were often wrathful of humans and made it difficult to travel through certain lands. They were better known as guardians of towns, as they would provide warnings about floods or impending attacks. This often came at the cost that the Taniwha impose laws and restrictions, even isolating the town with dangerous currents to deter travelers from visiting. If the forbidden Tapu (Tabu) was ever broken, the Taniwha would become enraged and destroy everything around them until the protectorates begged for forgiveness. Some were often so enraged that humans would have to kill them to settle the dispute, and often were able to because they had better numbers. Sometimes interestingly, it is said that some humans can become a Taniwha, often maidens or friends who have formed a close bond, often it is to carry on the will of that Taniwha to continue protecting others after they have passed on.
Their shape and size is also associated with inland waters or the ocean, often taking on the appearance of a lizard like creature in any case, they were often lone in most of the inland waters, but in the ocean they were much larger and traveled in groups.