Bearing in mind the fallibility of witness evidence this detail suggests there
may have been some mechanical issue with the heli prior to the ditching. Initially it seemed a little confusing as to whether 'sparks' occurred at the ditching itself, but later in the clip the witness appears to say it was at the apogee of the flight?
Somewhat more useful than the ABC's video at least, that was a waste of bandwidth from which I learnt nothing...