David Pate is the Executive Producer of News and Current Affairs for CBC Nova Scotia. Whenever he has time, he heads underwater.

As soon as the divers hit the water in Pictou Harbour, it's obvious that the mysterious shipwreck below is not going to give up its secrets easily.

The wreck was discovered by accident during a recent survey of the harbour by the Canadian Hydrographic Service.

No one knew it was there, or anything about it. That prompted local diver and wreck enthusiast Rob MacKay to mount an expedition to survey the wreck and try to solve the mystery.

MacKay invited a small group of divers to join him on his wreck hunting trip. I was lucky enough to be included on what for scuba divers is the trip of a lifetime: to be the first people to explore a previously-unknown wreck.

As we head for the dive site in the middle of the harbour, just a few hundred metres from the wharf, everyone wants to know how such a big ship could have lain undiscovered for so long.

MacKay explains that despite being so close to shore, the wreck is in a part of the harbour that's rarely visited. He also warns us to expect poor visibility because of silt floating in the water.

The descent to the wreckage shows that MacKay was right. The water is cloudy, like a yellowish fog, and the wreckage looms suddenly out of this soup.

We arrive close to the stern. I can only see one other diver, directly below me, a dark shadow in the gloom only made visible by his dive light.

I start swimming along the side of the ship. Every part of it is covered with anemones and other sea life, red, white, yellow and orange.

The hulk of the ship is wooden and mostly eaten away. Some iron superstructure remains, along with debris scattered inside the hull.

At the stern, there is a massive rudder and twin propellers. We now know this was a steamship.

Inside the hull, we find sections of what looks like piping, probably part of the engine, but there is no sign of the boilers.

I drift out to one side of the wreck to see if the boilers are nearby. Visibility is only about four feet and the ship fades away into the yellow water.

There is nothing to see on the bottom of the harbour except silt. I stick my hand down into the muck as far as my elbow. It's impossible to tell how deep the silt is.

As I pull my hand out, the silt spins around me. I can't see anything except the cloudy ocean. My light is useless, the beam reflected back by the particulate floating in the water, so I turn it off.

I have no idea where the wreck is but know it can only be a few feet away. There is no sign of the other divers.

I start swimming in expanding circles until I find the wreckage again and follow it along until I see the lights of my dive buddies.

Local wreck enthusiast Rob MacKay mounted an expedition to survey the wreck. (David Pate)

This is not a deep wreck. I log a maximum depth of 13.5 metres, around 45 feet, with some of the structure rising six metres from the bottom. There is plenty of time to explore.

But we are not here just to look: we want to find out more about this ship.

I tie a long line on a reel to the stern of the ship. Another diver heads to the bow, towing the line. We want to know how long the wreck is.

We already know that it's a big ship. At the bow, we find where the anchors are buried in the silt.

This raises more questions.

Was the ship anchored when it sank? No ship owner would want to lose valuable metal anchors and propellers. That seems to indicate that the ship was not deliberately sunk.

And close examination of some of the exposed wood shows evidence of charring. It's possible there was a fire.

Back on board the dive boat, we share our information. We now know the boat is about 60 metres long. That's bigger than the navy's Kingston-class coastal defence vessels.

How could such a big ship have disappeared from the records? And how long has it been down there?

There are some clues. The fact that it is a wooden-hulled steamship with twin screws point to it being late 19th or early 20th century, although some wooden ships were built during the First World War because of steel shortages for commercial vessels.

Every part of the ship is covered with anemones and other sea life, red, white, yellow and orange. (John Tapper)

The remains of a forecastle and superstructure at the stern, with a long flat area in between, shows that it was almost certainly a cargo ship.

Robert MacKay estimates that it's at least a hundred years old. And given the amount of silt sitting on top of the wreckage, it's clearly been down there for decades.

But we don't know the name of the ship, or where it was built.

Professional diver and amateur marine archaeologist Harvey Morash was the first of our divers to see the wreck. He was astonished at the state of such an old ship. Most wrecks in Nova Scotian waters are quickly ripped apart by storms.

Surprisingly intact

This vessel is lying upright and surprisingly intact.

"The most likely way to identify the ship is to find a manufacturer's name on a propeller or piece of the engine," he says. "That will help find out where and when it was made."

There was no time on this trip for such a detailed search. The poor visibility and the fact that so much of the wreckage is covered with growth will make the painstaking search for identifying marks a challenging one.

That's a mission for the next team of divers.

It's been an extraordinary first day of exploration in this virgin wreck, one that most scuba divers will never experience.

The only complaint on the boat is about the poor visibility and how it hampered our ability to see more of the vessel but Rob MacKay doesn't agree.

"That was some of the best visibility I've ever seen in the harbour," he says. "It was amazing, just amazing."

We head back to shore with MacKay already planning his next trip. He clearly won't rest until he finally solves the mystery.