It's your only window of opportunity when stuck in a sinking vehicle.

Forget the cellphone or even opening the door -- undo your seatbelt and open or smash the window next to you.

That's what a University of Manitoba expert on vehicle-in-water escapes is urging drivers to remember, to avoid the kind of mishap that claimed the life of 21-year-old Brandon woman Ashley Neufeld and two other women on Sunday in a pond near Dickinson, N.D.

Whatever you do, don't even touch your cellphone, said Gordon Giesbrecht. If you begin to make a call, you're almost surely going to die.

"Your window of opportunity to get out of the vehicle is the first minute," Giesbrecht, a professor of thermophysiology, said yesterday. "And the window is the way out."

Vehicles generally float for about a minute after entering water, he said. That's the moment drivers and their passengers must think clearly and immediately ensure everyone's seatbelts are unfastened before doing anything else.

Then get everyone into position, as best you can, to exit through the windows -- hopefully while the vehicle remains above the surface. If it's already sinking, the windows are still the only way out.

Until the vehicle fills with water to equalize the pressure, its doors won't open.

"After you've undone your seatbelt, you have to get the window open right away -- either open or broken," Giesbrecht said, noting the importance of keeping a centre-punch -- such as the Res-Q-Me device -- within easy reach if the water has shut down the power controls.

"The only sure-fire way to have an open window is to break it."

Giesbrecht has conducted about 80 experiments involving vehicle-in-water escapes, and presented seminars on the subject in the past couple of weeks in Brandon and Thompson. He estimates about 40 people become trapped in sinking vehicles in Canada every year.