Long ago before there was a great lake, a Chief cal Maahu lived with his wife and eight children. His people drew their water from two springs: Waikotikoti and Te Puna a Taupara. Waikotikoti was very tapu (sacred) and the water from here was used for sacred purposes only, while the other was for general domestic use.
One night the chief sent all his children to fetch water to quench his thirst. However, six of his children brought water from the sacred spring which was closer. When the chief discovered this he flew into a range and turned all six to stone. Meanwhile Haumapuhia, the remaining daughter, went searching for her father to give him the waster from the domestic spring. She found him at the sacred Waikotikoti.
When her father saw her arrive, he thought she too planned to collect water from the sacred spring. Outraged he grabbed her and thrust her under the water intent on drowning her.
Knowing she had no chance against her father's might she cried out to the gods of the land for help then heeded her pleas and turned her into a powerful Taniwha (water spirit). As a Taniwha, she knew the light of day would bring her death so she tried to escape to the sea where she could hide in its depths.
She set out north but was barred by the Huiarau Range, and so the Whanganui Inlet was gouged out. Next she thrust eastward and the Whanganui ō Parua arm was formed. One by one the arms of the lake were carved out in this fashion until she finally managed to force her way through a narrow gorge at Te Wharawhara near Onepoto.
As she emerged she was overtaken by daylight and turned to stone. She still lies in the bed of the Waikaretaheke River.