Understandably, the focus of this thread has been drawn to the harnessing of the passengers, and it is difficult to escape the conclusion that it played a major part in restricting their egress from the aircraft, with tragic consequences.
There are a couple of other aspects of the incident which seem to me to require further consideration though, none less so than the proposition that the fuel cut off could have ben accidentally operated by a passenger strap / harness of some sort.
I should say at the outset that whilst we have yet to have this proposition confirmed as the cause of the engine out, I am interested that nobody here has suggested that it is not possible or is even improbable. Certainly, with 5 PAX harnesses, and assorted camera and iphone tethers, there would be no shortage of snagging opportunity, and the photo reproduced earlier clearly highlights that there is much in the between seat area upon which to snag.
The fuel cut off lever would be just one of the potentially catastrophic options (and for those advocating twin engine aircraft as a mitigant, cutting off their fuel would have much the same outcome as here) : None of the Rotor brake, fuel flow, or collective would benefit from a sharp uncommanded tug in flight.
It is surely entirely foreseeable that something could snag a critical control in flight, and entirely reasonable that they should have been shielded or protected in some way?
Secondly, there is the question of the inherent risk of operations of this nature. Regardless of the quality of the safety briefings, these excursions were taking civilians into an inherently hostile terrain in the event of aircraft failure, with the most likely emergency landing venue being on water at a dangerously low temperature. The facts that they were tethered to the aircraft, and were not wearing immersion suits dramatically reduced their survival prospects from the level which they would otherwise have been at, which was itself by no means 100%.
Risk taking is unavoidable, and sometimes thrilling, but in this case it strikes me that the passengers could not have properly appreciated the risks they were taking, and the operators could.