Whatever the cause, the consequences are tragic. But for every accident of this magnitude there are many others that have significant effects on those involved, even if they don't attract the media coverage that this one has.
I work at the Wessex Neurological Centre, co-ordinating charity fundraising for the unit, and we see them all, be it head injuries from a swinging boom, a swimmer struck by a PWC or someone chewed up by a prop. More often than not, such injuries are not fatal, but the long-term effects of such head/brain injuries are often profound. Nobody sets out for a day on water with the intention of putting themselves or others in danger, but my guess is that most of these 'accidents' are avoidable.
For my own part, I won't let anyone board my boat without donning a LJ before stepping off the jetty and briefing anyone new aboard as to basic safety. Have I ever forgotten to attach the Killcord before setting off? - you bet I have, and it's a sobering thought when I have realised as I know precisely what the consequences could be.
It won't bring back those who lost their lives, or had them changed forever in Padstow on Saturday, but if PBR's stickers stop just one such accident from happening in the future then it will have been well worthwhile. I'll be applying one of as soon as I can get hold of one, and I applaud them for the initiative.