"And I thought it would make a great piece for Coast New Zealand so I approached them."
The response was positive, and he was invited to put the piece together.
Mr Carter said few people would have heard about the visit of U862 to the region's waters and was delighted to be part of the programme to tell the "intriguing" story.
The tale of the U862 is a colourful one, and included a whimsical chapter involving members of the crew clambering into a small boat and rowing ashore to Awatoto - and to a nearby farm where the submarine skipper Kapitan Timm later alleged they milked a few cows as they wanted fresh milk.
The story however was simply a piece of whimsy and was later recanted, but it added flavour to a remarkable story about a remarkable time, late in the war.
Mr Carter had heard that tale and laughed about it.
"There was no way they would have gone ashore - they would not have been that brave."
While U862 was off the Napier shoreline it surfaced at night, and the crew were able to head up to see the lights of the town glistening, and could hear jaunty music being played.
As they were only 200m offshore they could also make out people dancing and skating, at what historians believe to have been at the Sound Shell colonnade.
"It might have still been wartime but we had all our lights on."
The U862 has sparked plans for another potential visit back to the Bay as there is something "down there" he would like to find.
The torpedo.
He said he had diving and scientific colleagues who had specialised equipment like underwater magnetometers which could home in on steel items, as well as small submarine devices to go hunting it.
"I want to come back and go looking for it - one day," he said.
"It's on the list, definitely."
Mr Carter said the television timing of the Hawke's Bay sub story was spot on, as this weekend he would be in Sydney where he and another diver had been granted permission to dive in a restricted zone where the remains of a Japanese midget submarine lies.
It is 75 years since the submarine had gone down after an attack mission in Sydney waters.
The story of U862 and its errant torpedo is one of several parts of next Monday's episode which centres on Hawke's Bay's unique coastline and the occasional hidden (explosive) treasure, with host Neil Oliver steering a path to the Cape Kidnapper's sanctuary where he gets up close and personal with giant weta and a tuatara.
One of the show's other hosts, Hamish Campbell, steers a different course - toward what he describes as a "silver lining" from the devastating 1931 Hawke's Bay earthquake.
The quake's lifting of the terrain cleared away the waters, and the crabs it had been hosting, across a swathe of inland Bay View and today, as he discovered, part of that land is home to the appropriately named Crab Farm Winery.