The mood at the beginning of "The Swimmer" is languid and somewhat humorous. The story begins by describing the members of the church and even their priest as having a little too much to drink the night before.
"The pool, fed by an artesian well with a high iron content, was a pale shade of green. It was a fine day. In the west there was a massive stand of cumulus cloud "
The preceding description, with its pale green and soft approaching clouds, in the second paragraph continues this languid feeling within the text.