Prevention of these incidents in humans entails several measures. First, one must be safe in and around water. This includes close and continuous supervision of children within arm’s reach--whether or not a lifeguard is present. Second, one has to recognize distress and ask someone to get help. Third, in order to hinder sinking, someone present can provide flotation [1, 2].
Swimming lessons are beneficial for prevention. So are life jackets. Moreover, fences also have a role in obviation [1, 2].
When someone attempts to rescue a swimmer in distress, he or she must not also become a victim. This can occur when currents or deep water which brought the first victim under are still present. This also applies to certified lifeguards who can toss something that floats or use a pole to pull in the person [1, 2].