Does anyone know the source, the last verse & final chorus and the title of this song? I heard it at a festive gathering, and when I later tried to write it down I found I had to use the spit'n glue of less effective ,I think, words and phrases to fill in the gaps in my memory.

When I was a lad in a fishing town
an old man said to me,
You can spend your life, your bloomin' life
Sailing on the sea.
You can search the world for pretty girls
'Til your eyes grow weak and dim,
But don't go chasing those mermaids, son
if you don't know how to swim,

Cho: For their hair is green as seaweed
And their eyes are blue and pale.
And I'll tell you now before you start
You may love that girl with all your heart
But you're just gonna love the upper part
You are not gonna like the tail.

Well, I signed on to a sailing ship
And my very next day at sea,
I spied a mermaid in the waves
Calling out to me:
"Come go with me to the bottom of the sea
And down on the ocean floor,
I'll show you a million wondrous things
That you never have seen before."

So over I jumped and she pulled me down,
Down to her ocean bed.
And a pillow made of tortoise shell
She lay beneath my head.
She fed me shrimp and caviar
All from a silvery dish,
And her upper half was just my taste
But her bottom half was a fish.

(From this point the mermaid levaes, and the sailor laments his loss until he encounters a sea creature whose top half is a fish and whose bottom is a woman. The last line approximates:"I didn't give a damn about the upper half but I sure did love the tail."