Do you just NOT wear life jackets on a boat?????
For better or for worse, swimmers can get pretty blase about the need for life jackets and usually dont wear them. All of my children are strong swimmers and though their water experience is limited to pools, lakes and creeks, need to get beaten (figuratively) before they will put them on- even when it is required by law to do so. Despite the figurative beating, they keep looking for excuses to them off.
That aside, this incident is so awful as there are no survivors from an entire family. I cant imagine what that must be like for the relatives.