I agree people do panic in situations like that, but for the life of me I cannot see under what circumstances fiddling around for your phone and calling someone is your first reaction. I would've thought basic human instincts would've made you think "shit I gotta get out of here", not "shit there's water flooding in, better call someone to help".
Well it depends on what strategy you took, you'd likely be just as dead if you followed your instincts and busted yourself trying to open the door before the car's full and the pressure has equalized.
There were a number of TV shows where a escape technique was demonstrated were it stressed the importance of letting the car fill.
[video=youtube;2YaMEW30bv4]https://www.youtube.com/watch?v=2YaMEW30bv4[/video]
If you can't open the windows you are basically stuck while the car fills up with water. People have died calling 911 instead of making any escape attempt but once you're in the situation of the car filling with water and your plan is to get out the door I'd say what the Hell. I'm sure some poor bugger has died googling "escape from submerged car".
Actually looking
here what is recommended is getting a window down or broken and getting out as fast as possible. Making the point you'll often have no idea what depth the car will sink too or how it will be oriented. I was assuming the cars electric windows would rapidly be out of action turns out this isn't so, they should work for a couple of minutes.
It does not sound at all easy and faced with a car filling with water as you roll down a boat ramp into deep water, it's not actually intuitive to let more in, I think most people would be dead.