The majority of accidents involve personal injuries and/or fatalities, although the strong and continuous improvement in the field of accident prevention is resulting in a constant reduction of the number of marine related fatalities. After investigating several hundred marine accidents, we are concluding that marine accidents involving equipment failure have relatively low influence in the rate of personal injury accidents. Common accidents resulting in personal injury are caused by a condition not easy to detect by a casual observer. Hence, designers and supervisors should be alert and not to take for granted that a casual observer would recognize a dangerous situation.