Implicitly, the description of Jerry's longing to be accepted by the older, local boys in the wild bay, help to show that he has begun the process of growing up. "To be with them, of them, was a craving that filled his whole body [....]. They were big boys --...
Implicitly, the description of Jerry's longing to be accepted by the older, local boys in the wild bay, help to show that he has begun the process of growing up. "To be with them, of them, was a craving that filled his whole body [....]. They were big boys -- men to Jerry." His mother's company used to be enough for him, but now it is not. He wants to "be a man," to fit in and be accepted by those older boys that he sees as "men." Their acceptance of Jerry, to Jerry, makes him feel "happy. He was with them." This is the longing not of a child, but of a person making the transition to adulthood.
Further, the description of his first conversation with his mother implicitly shows that Jerry has changed and is beginning to mature. He longs to go to the "wild bay," away from the "safe beach" where he and his mother have always gone in the past. But "Contrition sent him running after her. And yet, as he ran, he looked back over his shoulder at the wild bay; and all morning, as he played on the safe beach, he was thinking of it." The wild bay seems to represent maturity and independence and freedom; the safe beach stands in for protection and childhood.
More explicitly stated, "that other [safe] beach, [...] now seemed a place for small children, a place where his mother might lie safe in the sun. It was not his beach." Unless Jerry were growing up, their original beach would have remained perfectly acceptable to him as it has always been. It is the change within him that now makes it seem like an inappropriate place for him.
Moreover, when he went to the wild bay again, "He did not ask for permission." A child asks permission; an adult does not.
Further, though he thought he might be able to make it through the tunnel at this point, he decides to wait. "A curious, most unchildlike persistence, a controlled impatience, made him wait." Children often struggle to delay gratification; when they want something, they want it now (much the way Jerry begged for the goggles he needed earlier). Adults, however, are supposed to be better at delaying in this way; a sign of maturity is one's ability to wait to gratify one's desires. Jerry now exhibits this kind of ability.