line breaks added from doument source....

HALFWAY ROCK

Halfway down the Cape Cod Bay
there sits a rock where the Indians say
An old man lives who knows the way
of the ocean and the sky
And they think it's wise a coin to throw
to the Halfway Rock and the man below
That calls the goodly wind to blow
and makes the vessels fly

HALFWAY ROCK & WE'RE BOUND FOR THE BETTER WEATHER
HALFWAY ROCK & WE'RE BOUND TO CROSS THE SEA

And once there was a man who came
from Halifax, Big Jim by name
Who laughed and said, It's all a game,
and he sat on Halfway Rock
He went to sea and there he drowned,
the waves did drag his body down
And tossed him up on the sandy ground
below the Halfway Rock

-CHORUS

So come all you lads and list to me,
don't ever venture out to sea
Without a copper penny tossed
to the man at Halfway Rock
If there would be a stock in trade-
a penny spent is a dollar made
A fair one sure if the penny's paid
to the man at Halfway Rock

-CHORUS

X:l
T:Halfway Rock
M:C
K:C
"Am" e e g g e e d c |"Dm" d d d c/d/ e d c A|
"Am" c c c c d c A G/A/| c A "Em" G G "Am"A3 c/d/|
e e g g e e d c/c/|"Dm" d d d c/d/ e d c A|
"Am" c c c c d c A A| c A "Em" G G "Am" A4||
"Dm" d2 c2 "Am" A2 G A|c G/G/ G G "Dm" A2 "Am" A2|
"Dm" d2 "Am" c2 A2 G A|c G "Em" G G "Am" A4|

I don't have any notes as to who wrote this.
It does sound right that it was on a PBS documentary.Also,I'm guessing on the melody - I didn't notate or chord it very thoroughly.
Am trying to learn ABC so let me know if it makes sense.