Here's what happens:
* Buck is in danger: Buck is caught in a raging river, struggling to stay afloat. He is about to drown.
* Thornton's heroic act: Seeing Buck in danger, Thornton jumps into the freezing water and rescues him. This act of bravery and devotion to Buck is significant because it solidifies their bond.
The significance of this event: This moment marks a turning point in the story. It symbolizes the deep connection between Buck and Thornton, a connection that transcends mere ownership. It shows how Thornton sees Buck as more than just a dog, but as a companion and a being worthy of his love and protection.
So, while Buck is often depicted as a strong and capable animal, it's Thornton who saves him from a watery grave, further demonstrating the powerful bond between them.