Bess Walder, 15, was fleeing the infamous Nazi aerial blitz of London in 1940 when her ship was hit by a German torpedo.
She was among many British children aboard the SS City of Bernares, an ocean liner carrying 406 people to safety in Canada.
The ship sank in less than 30 minutes. For nearly 20 hours, Walder and a friend clung to an overturned lifeboat on stormy seas. They were among just 108 people who survived.
Tom Nagorski, author of the new book Miracles on the Water, chronicles the disaster by piecing together survivors' tales — including the story of his own great uncle, Bohdan Nagorski. Tom Nagorski and Walder (whose married name is Bess Cummings) talk to Michele Norris about the chaotic events and heroic rescue.