I suspect your wits leave you extremely quickly when it happens - Adam Savage said it was incredibly unsettling to be in the car when it went in the water, and that was in a controlled situation with a rescue diver in the back seat.

They do make actual hammers for this situation that also include seat belt cutters because that can also be an issue. That said, I can’t imagine that anyone practices with one since you’d have to replace your window after. I wonder if the Tesla glass can actually stand up to one of them.