HI David!
Sorry for the delay.
Not Only this specific scene but along the whole movie William changes a lot his personality. He was supposed to be a lawyer but he rebels against his mother wish and go after his dream. At the beggining of the movie he is naive and he thought that he could trust in everybody. However he learned that people can be mean.
When I was a kid I broke my teeth jumping into the pool. My father used to say all the time "do not jump into the pool". And I insist tell him that it wasn't dangerous at all. But after that day I always obey my father's rules.
It was a great class.
Thanks all