Without having seen the episode, I wouldn't expect either of those to be good tools for breaking glass, regardless of whether you are underwater. Did they do any above-water control tests?
Neither did they. They were looking at the most likely options for the "ordinary" person. Keys, cellphone, and try to kick it out.
The Life Hammer strike looked more like a hard tap than a swing. The window broke instantly.
It sounds to me as though it would be better to break the window first, and unbelt yourself and others afterwards.
Unless you run out of air before you get your kid out of the child safety seat in the back (or your panicky/unconscious passenger out of their belt), under stress, with water blasting in through the open window . . . .
I've seen "official" statements that say to get everyone out of their belts, THEN open/break a window. That gives you the maximum amount of time before you have to start holding your breath.
How is the tip of a center punch much different than the tip of a knife?
If I had a Ritter Grip with me, I'd try using it closed. There's a steel angle at end of the thumb-ridges which looks like it would be enough of a point, while still being strong and hard enough, and with much less risk of cutting something. [/quote]If I couldn't get my Res-Q-Me or my Life Hammer, I'd go for the awl on my Leatherman.