Once more to the Lake by EB White questions.?

Question

I do not understand the end at all....

He describes how after the thunderstorm he “languidly” watched his son pull on his swim suit with no thought of going into the lake himself: “I watched him, his hard little body, skinny and bare, saw him wince slightly as he pulled up around his vitals the small, soggy, icy garment. As he buckled the swollen belt, suddenly my groin felt the chill of death” (202).

What happened?

Answer 1

EB White realizes, as he looks at his son, that he himself is getting older; he is no longer active enough to go swimming himself, and his son is growing up (symbolically, to take his place in the world after he dies)