Water plays havoc with electronics in modern cars
Many of the advances designed to make today's vehicles safer on the road can work against them when they get into water.
Water plays havoc with the sophisticated electrical and computer systems on modern cars and in a submerging vehicle, that usually means doors and windows can't be opened.
Tough, laminated windscreens and door glass also make it difficult to break out of newer models, effectively shutting down critical exit points.
"Once water gets into the engine bay of most cars these days everything shuts down," said Declan Allen, lecturer in Transport Engineering at the Dublin Institute of Technology.
"The electric windows are unlikely to work if the electronics get wet. Doors won't open until the pressure is equalised - so a vehicle has to sink until the water inside is equal to the pressure outside.
"Laminated windscreens are hard to break as well, as are door windows. In older cars you could push out a windscreen or break the side doors. "But with new and toughened laminated glass now it is extremely difficult to break them. Windscreens are really tough."
Additionally, salt water can have a 'conductive effect' - which means it can short out the electronics on a car more quickly than fresh water.
The pressure of the water on the windows and doors can be far too much for the electric window motors too - and even for manual (wind-up) systems.
Liam Cotter, consultant motor engineer assessor, based in Cork told the Irish Independent the electrics in a modern car would be destroyed as soon as there were a few inches of water in the cabin.
That is because so much of a car's electrics are routed through what is called the Body Control Module. As this is located on the floor, just under the carpet, it is immediately prone to being destroyed by relatively smaller quantities of water. The result is doors and windows can't be opened.
"All components would be wiped out as soon as there is a relatively small amount of water," he said.
He pointed out too that seals on doors, windows and other areas are designed to keep out rain but are not capable of coping with the enormous pressure of water on the outside.
"No car is waterproof. There would be a steady trickle and soon you'd have a foot of water."
He added: "And there is no human being that could press against the doors to open them even if the water was only a couple of feet up the door. The only chance of getting out a car is to get out the side windows."
But even that is no longer feasible in many cars as some have extra thickened glass or double glazing.
Mr Cotter added that there was no universally correct way to go about getting out of a submerging car.
"So much depends on the individual circumstances - the angle and speed of entry, for example. What is right in one case might be wrong in another."