He was scared because there was know on there with him. He didn't like to be by himself with out his mom right beside him the hole time. As Jerry was trying to achieve his goals of swimming though the tunnel he became more mature about thing. For example, "On the day before they left, he would do it." (481) Jerry was acting mature when he said the day for the left he would swim though the tunnel even if it killed him. Which that means Jerry set a goal and is not going to give up on it until he swims underneath the tunnel. Another time Jerry was being mature was when he said "He must go on into the blackness ahead, or he would drown." (483) Jerry was being mature when he was swimming and was heading into the blackness. As Jerry was drowning he head started to swell and how lungs started to crack. Jerry also show mature when he was keep holding a rock in his hands go he can hole is breath