In "Through the Tunnel," why is Jerry so determined to swim through the tunnel?
After his rejection by the older native boys, who have perceived him as immature as he splashes foolishly in the water, Jerry sits on the rough rock and cries "openly" because he envies their camaraderie and freedom and daring. So, after having "cried himself out," Jerry swims back to the beach where his mother sits, and demands swimming goggles, nagging her until she takes him to a shop and purchases them.
Equipped with the goggles, Jerry returns to the large barrier rock where he dives down to the base of this rock, but he can find no gap in it. Nonetheless, he perseveres until he does discover the hole that the boys have entered. And, because the rejection of the older boys has made Jerry feel childish and inadequate, he feels he must be able to go through this hole himself as they have done. Therefore, he secretly practices holding his breath until he becomes confident that he, too, can swim through the tunnel and, thus, in this "rite of passage," feel the older boys' equal. In addition, Jerry must prove his manliness to himself as well, so he challenges himself in facing the danger of swimming through the tunnel.
As he swims through the dark tunnel, "[V]ictory filled him. But, soon his lungs begin to hurt and he know that he must continue in the darkness or drown. Finally, while he lapses in and out of consciousness. Jerry makes his way into the open sea and struggles onto the rock where, exhausted he lies for a time. When his heart quiets down and his eyes clear, Jerry sits up and watches the other boys; this time, however, he does not need them because he has attained maturity and independence:
[H]e did not want them. He wanted nothing but to get home and lie down.
With determination, Jerry has proven to himself that he can do what the older boys do; he, too, is manly and not a child, anymore. He returns home and proudly tells his mother that he can hold his breath for nearly three minutes.