Neddy is alive at the end of "The Swimmer," so what happens to him after he finds his house for sale and family gone?
This story is full of wonderful themes like illusion vs. reality and alienation and loneliness. Neddy is an interesting character because he prides himself on being a little "odd" and because he has this vision of how others see him and how he sees himself. What is ironic about Neddy's journey through the pools he swims is that he gets lonlier the more he swims! He is utterly alone and cold and wet by the time he arrives home. There is no one there and the reader is left with him pounding on his door although no one is home.
Personally, I see Neddy having a complete and utter breakdown. I don't find him to be a particularly redeemable character, so in my opinion, he is reaping what he has sown, so to speak. He is now going to pay for the attitude he has had and for the affairs he's partaken in, among other things. This episode at the end is only the beginning of his miseries.