Kamaikaahui

Kamaikaahui was a person in Hawaiian myth. He was born in Maui as a rat, then he became several bananas, and then eventually he transformed into a man with a shark mouth on his back. To hide the shark mouth on his back, he always wore a cloth covering it. He kept the form of a man on land and took the form of a shark on the sea. He lived and farmed by the main road and would warn people of sharks as they would walk by going to the ocean. He would then take a shortcut and eat them in the form of a shark. People eventually start to suspect him and when he saw the large angry mob formed at the shore ready to kill him, he just swam off to another island. He ruled as a chief and terrorized people in the form of a shark for several years until he was killed by Palila, a folklore hero and a Kupua.

Citations:

Beckwith, Martha Warren. Hawaiian Mythology. United States, University of Hawaii Press, 1976.