Through the Tunnel by Doris Lessing

Jerry
Jerry is an eleven-year old English boy on vacation with his mother on a beach they have frequented in the past. Jerry's mother is a widow and is sometimes overprotective, sometimes not protective enough, of her son. Jerry attempts to make friends with some older boys on the beach, but they ignore him after discovering he is childish. Jerry is jealous of the older boys—he watches them as they swim through a rock in which there is a narrow underwater gap. In an attempt to become equal to them, he begins to persistently practice holding his breath so that he too may swim through the rock. He is determined to be able to hold his breath for a sufficient time so he can accomplish this feat. For Jerry, without a father and rapidly approaching adulthood, this challenge represents his coming-of-age, and with his success also comes independence from his often overprotective mother.

Mother