In chapter 16, Karana describes herself as happy. What caused her mood to change?

When she finishes the canoe, she and Rontu take it for a test journey around the island. It is on this journey that Karana notices a sea cave near the headland. She rows in with the canoe to discover that it is connected to a series of passages that lead to her house near the spring. She is very happy about this discovery, since she can hide her canoe near home and use the passage as an emergency shortcut if the Aleuts come.