Originally Posted by
MarcK
You want something with a sharp point to break tempered glass. All my cars carry a
spring loaded center punch in the center console.
Yes, Mythbusters tested the center punch and found it to be very effective. They also tested several scenarios of cars falling into water and found them to be marginally survivable at best, and the worst case, with a car tumbling in flood water was deemed not survivable.
You can break a window but you have to get everybody out of the car, in dirty, possibly dark conditions, before they drown.
Its a mess.