Their son Vahi-vero was stolen by two wild ducks that carry him to a distant island where two witches Nua and Mere-hua imprison him.
Once Vahi-vero reaches adulthood, he falls in love with a water-nymph Tahiti-tokerau, whom he persuades to marry him.
The shark swallows them and takes them back to Kororupo where Tahiti-tokerau is buried head down in the sand.
As he nears Puna's land, he must overcome various monsters, including Matuku-tagotago, the shark that had killed his father, whom he cuts out of Matuku's belly.
Rata, with the help of his servant Taraka, finally kills Puna, rescues his mother and restores her to health.