I have an entirely unreasonable fear of getting stuck in my car as it slowly sinks, unable to open the windows. It makes me want to get hand-cranked windows.
According to Mythbusters [1] it's almost impossible to wind down the windows in a sinking car after it reaches a certain depth. Much better is to have a window breaker tool. You can have one which doubles as a seat belt slicer too.
[1] https://mythresults.com/episode72