Acts of war, equipment failures, and poor design have all been known to cause a shipwreck. Violent, stormy seas can batter almost any ship to oblivion. But the Coast Guard estimates that well over half of all reported maritime accidents involve errors of seamanship or navigation. Seamanship errors include things like the person in charge not paying attention, being careless, reckless, or inexperienced, going too fast, or not posting a lookout. When factors that are not direct operator errors-inadequately maintained equipment, overloading a ship with cargo or with people, a poorly trained crew-combine with bad judgment, an accident at sea can seem almost inevitable.

Many accidents result from of a series of events-a chain of error-that leads up to a catastrophe. A fire that was caused by a carelessly tossed match and that should be easily extinguished, for example, blazes freely because the firefighting...