Surviving a shipwreck can depend on a host of factors: whether the accident took place in calm or stormy weather, and at night or during the day; the competence of the crew in an emergency; the availability and condition of lifesaving equipment; whether the ship actually sinks and if it does, how much time it takes to go under; and how quickly rescuers can reach victims. Even the temperature of the water can be crucial. The immense loss of life on the Titanic, for ex- ample, was a function of a combination of these factors. The accident occurred at night, there was a delay of almost an hour before the lifeboats-too few for the number of passengers -began to be loaded, the closest ships were several hours away, and the waters of the North Atlantic were frigid.

Such dire circumstances doomed about two-thirds of...