The character of Jerry and his decision to swim through the tunnel so he can join the older boys is at the center of Doris Lessing’s story. The plot is resolved when Jerry succeeds and then realizes that being with the other boys no longer matters to him, and he also brags to his mother about how long he can stay submerged. Determination is necessary for him both to complete the swim and to have this epiphany.
Most importantly, the author shows Jerry developing a daily regimen of practice to improve his swimming. Jerry recognizes that breath control is the key factor, as he must hold his breath underwater—he had already counted how many seconds the boys were out of sight before resurfacing. He practices for several days in a different location and perseveres despite getting nosebleeds. He decides to continue the training and to make the effort, which requires him to get past his fear of drowning.