Don't hyperventilateAs you hit the water, a physiological reaction known as torso reflex will cause you to gasp for air. Force yourself to take slow, deep breaths. You'll begin to shiver violently and feel intense pain; try to remember that these are natural responses and not life-threatening.
As you bob in the opening you fell through, turn and face the direction you came from. The ice there was strong enough to hold you until this point, so it should be able to support you as you maneuver out. You don't have time to take a chance on other escape routes.
Lift and kick
Stretch your arms over the ice and shimmy your body up until most of your torso is resting on the ledge. (This way, if you lose consciousness before you're free, you won't slip back under and drown.) Now, as you pull with your arms, kick your legs dolphin-style to propel yourself out.
Once out, logroll to shore. Resist the urge to rub your arms and legs (which would send the cool blood from your extremities straight to your core) or gulp hot liquids (which would trigger a rush of blood to your skin). Strip, wrap your torso in blankets, and sip a tepid decaf beverage.
(via Wired How-To Wiki)