You just fell through thin ice. Struggling to get out, you keep a cool (no pun intended) head and remember the following article:
Roll away from the hole. Don’t stand up right away. The ice around the hole may be weak, so you want to distribute your weight over as much area as possible. Roll away from the hole or crawl on your belly until you are several feet from the hole. After that, you can crawl on your hands and knees until you are certain you are out of danger. Only then should you stand up.