In the old days
In the early 80's we used to fly North Sea as pax on S-61s and on long night flights the stewardesses would serve drinks all round. Like a fixed wing a/c there were no survival suits worn. How this has changed.
The last time in 2012 I did the BOSIET refresher helicopter evacuation course I found the re-breather apparatus a great help and should allow you about 20 or so usable breaths under water.
It will interesting to see as to whether the survivors were able to prepare and don theirs before the rotors stopped rotating and the hull inverted and of course the evacuate command issued.
I just wonder if more could have been done to retrieve the poor trapped soul which didn't make it out. But judging by the frame photos, the hull didn't appear to suffer much damage so a descent rate of less 500'/m would seem likely which makes you wonder about press reports by pax of the craft 'falling rapidly'.