In 1999, Swedish medical student, Anna Bågenholm, was skiing in Norway with friends when she fell through a frozen stream and became trapped under a thick layer of ice. Unable to free herself, and forced to wait for rescue, her body temperature quickly fell to 13.7°C (56.7°F) and she fell unconscious. 80 minutes later, Bågenholm was brought to the surface by rescuers, clinically dead. But that is not the end of Anna's story...

Sources:

-Aftonbladet- Her temp was down to 13.8 degrees

-Swedish-Norwegian co-operation in the treatment of three hypothermia victims: A case report, Scandinavian Journal of Trauma Resuscitation and Emergency Medicine

- Tjugofyra7, Clinically dead but Anna survived – My story can help others

-Another Day: Cheating Death