The latest search efforts for Jeffrey Boucher turned up no sign of the missing school teacher on Monday, a day on which his wife said she believes he is dead.

The Whitby, Ont., man was first reported missing three weeks ago, on the morning of Jan. 13.

Boucher, 52, went missing, apparently after going for his regular morning run.

On Monday, the missing man’s wife, Kristen Boucher, told CBC News that she and the couple's two daughters are preparing for the worst.

"Something weird happened to him obviously," she said. "Because if we can't find him, it's got to be something really strange. Whether it's that he's lying somewhere that we can't find or that hasn't been found yet, that's I guess where I need other people's help."

Jeffrey Boucher

A water search resumed Monday at the Whitby harbour for Jeffrey Boucher, who vanished without a trace nearly three weeks ago. (CBC)

Boucher said she believes there's a "zero per cent chance" her husband either ran away or committed suicide.

A search Lake Ontario resumed Monday for Boucher. Durham Regional Police used a robotic underwater camera on loan from the Toronto police to search the water along the Whitby waterfront. But as the day came to a close, police had found no sign of Boucher.

In the days after Boucher first disappeared, police conducted an exhaustive search of the trails and wooded areas near his home. Boucher was an avid runner, who jogged almost daily and often varied his route.

Air and ground searches were undertaken, but Durham Regional Police could find no signs of Boucher's whereabouts.

On Jan. 20, police said they were "truly stumped" about what had happened to him.

Police announced last month that a water search of the Whitby harbour would begin, but had to postpone the effort due to high winds and frigid temperatures.