BARRIE, ONT. -- Kevin O'Leary told a Parry Sound, Ont., court on Wednesday via Zoom from Los Angeles that the boat they hit in 2019 "was invisible."

The businessman and reality TV star's wife, Linda O'Leary, has pleaded not guilty to one count of careless boating after a two-vessel crash on Lake Joseph in 2019 that claimed the lives of Gary Poltash and Suzana Brito.

As the defence's first witness, Kevin O'Leary testified his wife was always at the helm, saying "she's a very good marine boater."

He said he was always by her side, keeping a watchful eye.

"I'm always looking forward," he told the court. "At night, I want to be watching forward, and I was that night as well."

O'Leary said the other boat, owned by Dr. Irv Edwards and captained by Dr. Richard Ruh, was "completely pitch black" before the collision.

Edwards and Ruh had testified the lights were on at the time of the collision.

Both men are being sued in civil court.

"There was no light," O'Leary said, adding he was surprised to see how big the boat was when the lights were turned on after the crash.

"It lit up like a Christmas tree. It was huge," he testified.

The questioning also touched on whether Linda O'Leary had consumed any alcohol during a dinner party before the collision.

Her husband said he didn't recall her having had a drink, though there were several hours when they weren't together.

He added that it would have likely been watered down if she did have a drink because she was driving.

"She would turn off any noise or music and just boat. Keeping very alert to what was around us," Kevin O'Leary told the court of his wife's boating habits.

On Tuesday, defence lawyer Brian Greenspan told the court they had yet to hear any basis as to why his client was responsible for the deadly crash.

Closing submissions are scheduled for Thursday, with the judge's decision expected to take several weeks.

With files from The Canadian Press and CTV's Mike Arsalides