What makes sense to me is a device inside the vehicle that doesn’t require a swing to strike the glass, such as a hammer would require. One of the spring loaded window punches makes more sense; press against the glass, the spring is activated and shatters the (non-laminated) glass. I have a Resqme Seatbelt Cutter and Window Glass Breaker dressed in yellow inside the car and another on my keyring. Break the glass and either open the door to swim out or go through the now open window (with increased risk of laceration).

In one run-thru in the video link I posted above they also started opening the door immediately on water entry which might work depending on the vehicle and mindset of the individual. Things go wrong at the worst possible time and the door not wanting to open after you are submerged would be typical... If the door won’t open on the surface, I’d immediately shift to breaking the glass.