Lessing's young protagonist is eleven years old and he is on vacation with his mother who is a widow. The story begins by explaining a conflict within the boy; he feels the need to stay with his mother out of duty but also wants to explore another beach on his own. The mother recognizes his desire to leave her side and permits it so she won't be too stifling to his growth. In fact, the author reveals the mother's thoughts by saying, "She was determined to be neither possessive nor lacking in devotion. She went worrying off to her beach."
The characters represent a real situation in life as a single mother strives to rear a son to become a man. Without a father figure in his life, she must play both roles and that can be difficult. Jerry's mother, though, does a great job by permitting him to go exploring on his own, but always being near for help if he needs her. After Jerry struggles through learning to hold his breath and daring to swim through the tunnel--and having gone through many headaches and nose bleeds in the process--his mother never over reacts or loses her composure. For example, Jerry tells his mother that he can hold his breath under water for two or three minutes and her reply is "Well, I shouldn't overdo it. I don't think you ought to swim any more today." Luckily, he was done with achieving his goals and agreed to stay out of the water.