One theme that is present in Doris Lessing's "Through the Tunnel" is the attainment of independence.
Jerry is an eleven-year old boy who is the only child of a widow. While he and his mother are on holiday together, Jerry yearns to be more like the older boys that he observes away from the beach where he usually goes with his mother. One day he suddenly blurts, "I'd like to go and have a look at those rocks down there." When she hears her son's words, the mother worries that she has possibly been too possessive, keeping him with her all the time. So, she gives her permission.
Jerry observes that the older boys—"men to Jerry"—dive down and swim through a barrier of rock; then, they emerge on the far side. Afterwards, Jerry yearns to be able to perform this manly feat himself. In order to be able to do so, Jerry practices diving down in the water and holding his breath and using goggles that his mother has bought for him. Through his daring perseverance, Jerry can hold his breath long enough to pass through the narrow end of the tunnel:
His lungs were beginning to hurt. A few more strokes and he would be out. . . . He was at the end of what he could do. . . . He must go on into the blackness ahead, or he would drown. . . . He felt he was dying.
Between lapses of unconsciousness, Jerry succeeds in passing through the rocky tunnel.
After this success, Jerry has gained his independence and individual identity. When he sees the boys diving and playing a short distance away, Jerry no longer desires to join them:
He did not want them. He wanted nothing but to get back home and lie down.
Later, since Jerry feels confident in his new manhood, going to the bay is no longer of any interest to him. Jerry is confident in his individualism.