Here are the chords used in this song

    B5      F#5      E5       C5       F5      G5
E------/---2---/---0---/---0---/---1--/---3---/
B---4--/---2---/---0---/---1---/---1--/---0---/
G---4--/---3---/---1---/---0---/---2--/---0---/
D---4--/---4---/---2---/---2---/---3--/---0---/
A---2--/---4---/---2---/---3---/------/---2---/
E------/---2---/---0---/-------/------/---3---/


Intro:   B5  F#5   E5   B5  F#5  x2

B5           F#5
Long ago I don't know when
E5                        B5            F#5
That's when they let the water flow in 
B5                        F#5
They said it's time, it's time to begin
E5               B5           F#5
So they let the water flow in


B5                          F#5
Let the water flow, let it flow right in
E5               B5           F#5
Come on baby, let's take a swim
B5                         F#5
Let the water flow, let it flow right in
E5              B5           F#5        E5     F#5   back to B5
Come on baby, let's take a swim in love


Verses are the same and choruses are the same.  On the key change
just insert C for B and G for F# and F for E.   Have fun even though
you probably won't have the 40 druken girls singing the last chorus
with you.  Enjoy.