I have read of several Instances where people have been left behind because of being on independent tours. I believe that it is true that no captain "wants" to leave anyone behind but there are times when no option is available. People are advised of what could happen if not back on time. Take all of the precautions that were mentioned but it is your responsibility to make sure you are back before departure. Do your independent tours, enjoy them just be aware. If by chance an unfortunate accident does happen that is where your trip insurance comes into play.