Mr McNamara took Cooper to the vet, but a decision was made to take her to Massey University in Palmerston North, where they have gear necessary for such a delicate procedure.
The fish-hook was lodged far down Cooper's oesophagus, near the heart, making surgery a dangerous and expensive option.
"She told me that if they had to operate, that would start at $4000.
"I said, whatever has gotta be done, do it."
Thankfully, surgery was not necessary. Vets were able to remove the hook using long tweezers with the aid of an endoscopic camera.
The procedure took three-and-a-half hours and cost Mr McNamara $2000.
It did not take long for Cooper to bounce back.
"We were pretty lucky.
Mr McNamara was not bitter towards people who fished in the area, but said some fishermen needed to be more careful with their hooks.
"Some of them leave their hooks and just don't worry about it. They probably don't think,'' he said.
Whanganui District Council issues $100 fines for littering. A spokesperson said they not aware of any other cases of dogs swallowing discarded hooks.