Though, this is another one of those quotes that demonstrates the unreliability, sometimes, to absolutely pin down the source. I am suspicious of the Shedd attribution, because even though he was a respected theologian, a Calvinist, and an author, all the attributions for him say that "he said." Well, if he wrote so much, why all of a sudden is he known for this quote that "he said."
When you search for the first part of the quote, almost all attributions go to William Shedd. When you search for the last part of the quote, all of a sudden you see tons of attributions to a John A. Shedd, and I cannot find out anything about this person.
If you look at the website I've included about Grace Hopper, it seems to me this is the best reference for a solid attribution available; again, on the Internet.
Someone with some hardcopy resources might be able to source it better. Oh, and the saying varies between harbour, harbor, dock, and port. (Geez, did I get all over this or what
"A ship in port is safe, but that's not what ships are built for," said Rear Admiral Grace Murray Hopper.http://niagara.rivier.edu/students/mneville/history/hopper.htm
A ship in port is safe, but that's not what ships are built for. Grace Brewster Murray Hopper. (The use of the word "bug" is also due to Grace Hopper. She traced a computer problem to a dead bug in the hardware and taped that bug into her notebook.) http://niagara.rivier.edu/students/mneville/history/hopper.htm
A ship in a harbour is safe, but that is not what ships are built for." - great nineteenth-century theologian, William Shedd
A ship in a harbour is safe, but that is not what ships are for. John A. Shedd.
A ship in port is safe, but that is not what ships are built for. -- Benazir Bhutto
"A ship in the harbor is safe, but that's not what ships are built for."
-- GRANT M. BRIGHT
Ships Are Safe in the Harbour (poem, author unknown)
All I live for is now
All I stand for is where and how
All I wish for are magic moments
As I sail through change
My resolve remains the same
What I chose are magic moments
Because ships are safe in the harbour
But that is not what ships are made for
The mind could stretch much further
But it seems that is not what our minds are trained for
We call for random order
You can't control Mother nature's daughter
Ships are safe in the harbour
But that is not what ships are built for
The witch hunter roams
The scary thing is that he's not alone
He's trying to down my magic moments
As we sail through change
Ride the wind of a silent rage
And sing laments of magic moments