How to survive if you drive your car into a body of water, according to survival experts

• After a Jeep was spotted submerged in a Texas lake, a woman was found alive inside.
• Survival experts said the woman probably had a pocket of air in the car.

A woman in Texas was lucky to survive after being pulled from a Jeep that was submerged in a lake, but there are straightforward steps a person can take if they end up in a vehicle in a body of water, according to survival experts.

A fisherman called police after spotting a black Jeep in Lake O' the Pines on Friday morning. Deputies with the Marion County Sheriff's Office were dispatched to the scene, arriving in about 18 minutes. After the wrecker service arrived to pull the jeep out of the water, the fisherman took them out in the water to hook onto the Jeep to pull it out.

"It was at that time they saw the woman," Capt. Chuck Rogers told Insider. "The fisherman and wrecker employee were able to help the woman from the jeep. They placed her into the boat and she was brought to shore."

The woman told authorities she thought she had spent several hours in the Jeep in the lake. But how exactly she ended up there, or how she survived, was not clear.

Cat Bigney, a survival expert who has taught at the Boulder Outdoor Survival School for decades, told Insider a vehicle in water is "an urgent survival situation" because brain death typically begins within four minutes of oxygen deprivation.

"Act quickly but don't panic. You may only have a minute to get out, but you must stay focused," Bigney, who has consulted for Bear Grylls and National Geographic, said.

SWOC: Seat belts off. Windows open. Out immediately. Children first.

Gordon Giesbrecht, a professor at the University of Manitoba, agreed that the first minute is absolutely crucial when a vehicle enters a body of water. Giesbrecht, who has been called Professor Popsicle, has studied cold water survival and the prevention of vehicle submersion deaths, even conducting his own demonstrations of driving a car into a body of water and what not to do in a sinking vehicle.

Giesbrecht explained there is a simple way to remember what you should do if you drive into water — SWOC: Seat belts off. Windows open. Out immediately. Children first.

"You've got about a minute to get out of the vehicle," he said, adding it was more than enough time if you act quickly and don't waste precious minutes panicking.

It may take several minutes for the car to sink, but it's important to get the windows open as soon as possible. As the water level rises on the outside of the vehicle, the resulting pressure can push into the windows, making them impossible to open, he said. Electric windows will continue to work for some time — it's the external pressure from the rising water that will quickly make the windows impossible to open.

If you are unable to open the windows in time, the next option would be to try breaking them. But Giesbrecht described that as nearly impossible. You can try to get creative with tools you have in the car, or use a tool designed to specifically break glass, but he said you shouldn't count on it.

Don't count on opening the door: 'Nothing good can happen after 60 seconds'

Giesbrecht also rebuked the widely held idea that you should wait for the car to fill with water, at which point the pressure on the inside and outside of the vehicle will equalize, allowing you to open the door.

When a car sinks, even if the windows are closed, water will get in through the vents and through the trunk, which is not airtight, unlike the doors in the passenger compartment. Although the trunk and passenger compartment are generally separated by a backseat, that barrier is also not airtight, meaning the two areas form one continuous air space, rather than two.

Typically, the passenger compartment will fill with water first, causing the car to go vertical, with the trunk portion up in the air as it sinks, until the remaining air escapes through the trunk and it also fills up with water.

Meaning, if you wait for the passenger compartment to fill with water, but the trunk isn't yet filled, there will still be more pressure outside than inside, and you won't be able to open the door.

"When the passenger compartment is full, the vehicle is not," Giesbrecht explained. "There's more pressure on the outside than inside because there's still air inside the trunk."

And if you try to wait until the entire vehicle, passenger compartment and trunk, is filled with water, you likely won't have enough time.

The bottom line, Giesbrecht said, is don't count on escaping that way, adding: "Nothing good can happen after 60 seconds."

As for the woman in the Jeep, he said there must have been an air pocket in the vehicle that allowed her room to breathe. He also noted that the Jeep was likely not fully submerged. Indeed, photos from the scene appear to show the very top of the Jeep just above the water. The Jeep also appeared to be horizontal, meaning the water was not deep enough to cause the vertical inversion that can happen when a car sinks.

"That woman was very lucky that her vehicle stayed horizontal and was in shallow water and somebody came by," he said, but added that, assuming she wasn't injured or unconscious, "she would've absolutely had time to invoke SWOC."

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