When a car falls into the water on Lake Ontario, the Toronto police marine unit says there's almost nothing they can do to help.

A woman died on Thursday afternoon after her vehicle plunged off a bridge and into an eight-metre deep shipping channel near Polson Pier.

Police announced they had located the vehicle approximately two hours after it went into the water.

"There's really nothing we could have done on our end to facilitate a rescue at all," said Const. Patrick McLeod, the marine unit's lead diver.

"Everything went textbook, totally textbook for this recovery."

A recovery team, not a rescue team

The Toronto Police marine unit is stationed just more than three kilometres from where the car went into the water on Thursday.

McLeod says that even if a team of divers had been geared up and waiting on a boat, a successful rescue would have been nearly impossible.

An adult in that situation will typically drown within two to five minutes, he says.

Police divers recovered the driver and vehicle on Friday after a car plunged off a bridge into Lake Ontario Thursday afternoon near Polson Pier. (CBC)

"For us to get to the scene and extract that person, it's not going to be done in minutes," he said. "It's going to take an hour, two hours for us to get mobilized, to get the right people in."

Anything else, McLeod said, is pure "Hollywood" fantasy.

To his knowledge, he said, Toronto police have never conducted a successful rescue of a sinking car in Lake Ontario.

Finding the car

Police located the vehicle with an underwater camera at around 6 p.m. Thursday. They shelved the recovery efforts about 30 minutes later, when the light started to fade.

"In a dark situation with a lack of daylight, officers are essentially going in blind," said Const. Clint Stibbe.

Even in the broad daylight, the divers had to be guided by radio once they entered the water, Stibbe said.

How to escape

With a rescue out of the question, police say a driver's best chance for survival is to stay calm and escape the car under his or her own power.

"You want to get those windows down right away, get your seatbelt off and get ready to go out the window," said McLeod.

If power to the windows has been cut, the next option is to wait for the car to fill with water, until the interior pressure equalizes with the pressure outside the doors.

"[The water] might be quite high before you're able to open that door and pull yourself out. So it's going to take a calm head and hopefully people can do that if they ever find themselves in that situation," McLeod added.