David Perry 
The Holiday Adventures of Bonza and Sonja [EPUB ebook] 
The Humpback Whales

This book is a description of where they lived and how they ended up in the Antarctic.
They were hoping one day to meet their sister Jenny, who lived on the other side of the freezing Antarctic. They said goodbye to their friends who were swimming to Hervey Bay, Queensland, where it is warm. They decided, after a few days, to go themselves. They were warned by their father to watch out for whaling boats, which they had a close call with. They passed by many sailing boats, ships, and bays. They also went past Botany Bay, and they rested at Bondi, close to the beach where the people were in awe of their breaches out of the water. They rested there before they moved on.