If you can’t get the windows down before the water pressure seals them shut, it’s still survivable without a glass breaker if you keep your wits about you and the car doesn’t flip. You’d need to take a deep breath right before the interior completely fills with water and then just sit there until the pressure mostly equalizes. There was at least one reported case of someone in a submerged car specifically crediting their survival to Mythbusters successfully showing just that, but a variation of the scenario involving the car flipping while sinking into deeper water later proved to be much less survivable.