What details does the writer include in paragraphs 8 & 9 to tell you about Jerry's personality?

"Through the Tunnel" is a coming of age story for young Jerry.  Readers are privileged to watch him gain mental and emotional maturity and independence.  Paragraphs 8 and 9 help establish Jerry's desire to gain some independence from his mother.  Jerry loves his mother, but he also desires to establish his own presence in the world.  Instead of being somebody's son, he wants to be his own person.  Paragraph 8 shows that desire.  

He ran straight into the water and began swimming. He was a good swimmer. He went out fast . . . 

Readers can see there isn't a hesitation in Jerry's movements away from his mother.  He's goes straight for the water and goes in fast and hard.  The paragraph shows that Jerry desires some freedom.  The paragraph also shows that Jerry is confident in his own abilities, and courageous enough to quickly move himself into a foreign and potentially dangerous area.  

. . . a middle region where rocks lay like discolored monsters under the surface, and then he was in the real sea, a warm sea where irregular cold currents from the deep water shocked his limbs.

Paragraph 9 shows that while Jerry does desire to be his own person, he doesn't yet have the courage to break all ties with his mom.  He still likes knowing that she is present in his life as a protector.  

He swam back to the shore, relieved at being sure she was there. . . 

Jerry may want to act tough and independent, but he secretly likes knowing his mom is there to protect and comfort him.