For the first few seconds, it doesn't look like a life-and-death situation.

A grey four-wheel drive ute enters floodwater covering a road in Morayfield, north of Brisbane.

The water appears mostly calm. There is no raging torrent, no dramatic wall of water.

But within minutes, the vehicle is gone.

It's a stark demonstration of a message flood safety experts repeat year after year: "If it's flooded, forget it."

While ABC reporter Will Murray and bystander Daniel Hainey pulled the driver free, the footage shows just how little time there is to escape a sinking car.

10:04am ThursdayA car drives past a "road flooded" warning sign on Buchanan Road.

Mr Murray and ABC camera operator Liz Pickering are on the scene to report on flash flooding in south-east Queensland. Almost instantly, they start running toward the scene, aware of the danger.But for the driver, there is little indication of how deep the water is.

According to UNSW senior research fellow in the School of Population Health Amy Peden, that uncertainty is precisely what makes floodwaters so dangerous."You can never know the velocity and the depth of the water," Dr Peden said.

Approx 30 secondsThe ute is stranded and starts to float after making it about halfway across the flooded road.

On her own camera tape, Ms Pickering is heard saying: "How can we help him? Jesus Christ."

Air trapped inside the cabin initially gives the vehicle some buoyancy. But water is already starting to infiltrate the vehicle's systems."As the water gets into the workings of the car, it will start to sink," Dr Peden says.

Mr Murray immediately calls Triple Zero (000), trying to pinpoint their exact location for emergency services.What began as a vehicle crossing a flooded road has become a race against time.

Approx 1 minuteThe car begins to spin. The bonnet is under water.The driver is trying to reverse out, with no luck. His window line is edging closer to the water's surface.

For anyone trapped inside, every passing second is reducing escape options."You need to try and get out of the vehicle quickly," Dr Peden says.

Approx 2 minutesThe rear wheel is fully submerged; the ute's snorkel is soon underwater.

Approx 3 minutesThe situation hits a tipping point. The car is sinking, and quickly.The driver is trapped inside what's rapidly become an underwater chamber.In the distance, bystanders are shouting.

What comes next is an extraordinary act of bravery. But Dr Peden warns such rescues can come at a devastating cost, with would-be rescuers sometimes drowning while trying to help.Her advice is simple: don't put yourself at risk, and call for help as quickly as possible.

Approx 3 minutes 30 secondsPassing the phone to Ms Pickering while still talking to Triple Zero, Mr Murray decides to act. He starts swimming towards the sinking car.Mr Hainey follows.

"When we got to the car we tried to open the closest door, no luck, then got on the back of the car with the thought to break the back window," Mr Murray said."I thought to try the passenger side rear door first and put my feet against the car and pulled as hard as I could, and with some luck the door swung open."As soon as the door opens and the driver comes out, the vehicle sinks completely.

It is only 90 seconds from the moment Mr Murray and Mr Hainey get into the water to attempt the rescue until the four-wheel drive's roof is submerged."I think what this vision very clearly shows is that you will not have a lot of time," Dr Peden says.

The driver, Mr Murray and Mr Hainey emerge safely.

The car disappears underwater.

Every second counts

For both flood researchers and emergency responders, the rescue demonstrates a simple reality: people often have far less time to escape than they realise.

Queensland Fire and Rescue swift water instructor Matt Kelemen says the first thing people should do if caught in this situation is take off their seatbelts and try to wind their windows down.

Even if the car's windows are electric, they should work for at least 10 to 60 seconds.

"Before the water comes up too much and shorts out the car's circuits, let the windows down so you've got an egress area out of the vehicle," Mr Kelemen says.

If that's not possible, experts say to try to find something inside the car to smash the window. But not just any window.

"Your front windscreen and your rear dash window are both laminates, so they're not the best to break because they'll just crack and they'll stay in place," Mr Kelemen says.

"But nearly every side window on all cars now is just tempered glass, so you should be able to hit it, and it should shatter."

You may be thinking, why not try to just open the door?

Well, opening a door against floodwater can be difficult because of water pressure acting on the outside of the vehicle.

Mr Keleman says occupants may effectively be trying to push against hundreds of kilograms of water, which is why emergency services encourage people to use windows as their primary means of escape.

No safety tools can remove floodwater risks

Research from the University of NSW Water Research Laboratory shows even relatively shallow water can cause vehicles to begin floating.

• A small car like a Toyota Yaris can be moved by water just 15 centimetres deep with a flow speed of 3.6 km/h. It can be carried away in 60cm of water.
• A larger four-wheel drive can be moved by 45cm of water and begin floating in 95cm of water, able to be pushed along by just a finger.

"Don't think because you've got a bigger vehicle, a more powerful vehicle, that you're going to be OK," Dr Peden says.

"The safest car in floodwater is the one that never enters it."

The Morayfield rescue ended with handshakes, hugs and relief. But the footage leaves a sobering lesson.

The driver entered the water in a functioning vehicle. About six minutes later, it had disappeared beneath the surface.

And without two brave bystanders, the outcome may have been very different.

• Reporting:
• Design, video editing:
• Production:
• Editing: