So this is a very simple song but a very emotional one, and the chords used in the song 
are as follows. The progression never changes:

G D Em C D Em D G

Same progression for the rest of the song, listen to it to get the cues of when to 
change on certain words.

Lyrics:
G
This summer I went swimming
D                       Em
This summer I might've drowned
Em                         C
But I held my breath and I kicked my feet
D                      Em
And I moved my arms around
D                 G
Moved my arms around

This summer I swam in the ocean
Then I swam in a swimming pool
Salt my wounds, chlorine my eyes
I'm a self-destructive fool
A self-destructive fool

*Banjo break*

This summer I did the backstroke
And you know that that's not all
I did the breaststroke, and the butterfly
And the old Australian crawl
The old Australian crawl

This summer I swam in a public place
And a reservoir to boot
At the latter I was informal
at the former I wore my suit
I wore my swimming suit

*Banjo break*

This summer I did swan-dives
And jack-knives for you all
And once when you weren't looking
I did a cannonball
I did a cannonball

This summer I went swimming
This summer I might've drowned
But I held my breath and I kicked my feet
And I moved my arms around
Moved my arms around

*Fiddle solo*

End