POPULAR MECHANICS: How To Escape A Sinking Car. “Rule 1. Don’t Call 911 until you’re out of the car. You’re going to need every second to get out of that vehicle. . . . Break that window. Since most vehicles these days have electronically controlled windows, the circuits probably will short before you have a chance to roll them down. In that case, you’ll need a tool to break the window open.”

They recommend the Lifehammer or the Res-Q-Me, both of which have been discussed here before.