In Doris Lessing's "Through the Tunnel," Jerry, a young English boy, and his mother are on vacation at a beach they have frequented many times before. Although the exact location of the beach is unspecified, it is suggested that they are in a foreign country. Both Jerry and his mother strive to accommodate each other without making excessive demands. Jerry's mother, a widow, is "determined to be neither possessive nor lacking in devotion," while Jerry acts out of an "unfailing impulse of contrition—a sort of chivalry."

On the second morning, Jerry expresses a desire to explore a "wild and rocky bay" he has seen from the path. His attentive mother allows him to go, attempting to appear casual, and Jerry leaves behind the crowded "safe beach" where he usually plays. Being a strong swimmer, Jerry ventures far enough into the water that his mother becomes a small yellow speck on the distant shore.

As Jerry looks back toward the shore, he notices some boys removing their clothes and running down to the rocks. He swims in their direction but maintains his distance. The boys are "of that coast; all of them were burned smooth dark brown and speaking a language he did not understand. To be with them, of them was a craving that filled his whole body." He watches the older and bigger boys until one finally waves at him, prompting Jerry to swim over eagerly. However, upon realizing he is a foreigner, the boys lose interest in him. Despite this, Jerry feels content simply being among them.

Jerry joins the boys in diving off a high point into the water. Then, the largest boy dives in and does not resurface immediately. "One moment, the morning seemed full of chattering boys; the next, the air and the surface of the water were empty. But through the heavy blue, dark shapes could be seen moving and groping." Jerry dives down as well and encounters a "black wall of rock looming at him." When the boys reappear on the other side of the rock, he "understood that they had swum through some gap or hole in it ... [But] he could see nothing through the stinging salt water but the blank rock." Jerry feels a sense of failure and shame, shouting at the boys first in English and then in nonsensical French, with a "pleading grin on his face like a scar that he could never remove."

The boys dive into the water around Jerry, and he panics when none resurface immediately. Only after counting to 160 do the boys emerge on the other side of the rock, and as soon as they surface, they leave. Believing they are departing to avoid him, he "cries himself out."

When Jerry meets his mother at the villa that afternoon, he insists she buys him goggles immediately. With the goggles, he can suddenly see as if he had "fish eyes that showed everything clear and delicate and wavering in the bright water." He dives repeatedly, desperately searching for the opening in the rock the older boys had swum through until finally, "he shot his feet out forward and they met no obstacle."

Determined to swim through the tunnel, Jerry begins practicing to control his breathing right away. He lies "effortlessly on the bottom of the sea" with a large rock in his arms, counting. That night, his nose bleeds profusely, and for the next two days, he exercises his lungs "as if everything, the whole of his life, all that he would become, depended upon it." When his nose bleeds again, his mother insists he rest with her on the beach. He complies for a day, but the next morning, he heads to the bay alone without asking, "before his mother could consider the complicated rights and wrongs of the matter." He practices holding his breath underwater, displaying a "curious, most unchildlike persistence" while studying the tunnel.

When his mother announces they will leave in four days, Jerry vows to succeed in his quest even if it kills him. His nose bleeds so badly he becomes dizzy, worrying that the same might happen in the tunnel, trapping him. He resolves to wait until the following summer when he will be bigger and stronger. However, an impulse overtakes him, and he feels he must attempt it immediately—now or never. "He was trembling with fear that he would not go; and he was trembling with horror at the long, long tunnel under the rock, under the sea."

Inside the tunnel, he begins counting, swimming cautiously, feeling both victorious and panicked. "He must go on into the blackness ahead, or he would drown. His head was swelling, his lungs cracking ... He was no longer quite conscious." Even when he surfaces, he fears "he would sink now and drown; he could not swim the few feet back to the rock." When he finally pulls himself onto the rock and removes his goggles, they are filled with blood.

After resting, he notices the local boys diving from a distance of half a mile, but he has lost interest in them. All he desires now is "nothing but to get back home and lie down." When he returns to the villa, his mother is worried about his "strained" appearance, but she reassures herself with the thought that "he can swim like a fish." He suddenly announces that he can stay underwater for "two minutes—three minutes, at least," and she responds in her usual calm manner, advising him that he "shouldn't overdo it." Jerry has achieved his goal—it is "no longer of the least importance to go to the bay."