From what I remember about this, there had been many complaints about the safety of the rescue service, following a number of accidents / incidents. So, in order to show just how safe they were, the army gave a demonstration of a water rescue.
I believe it went into the water due to pilot error, but I might be wrong on that. Unfortunately, the pilot then tried to take off again. Understandable, perhaps, but forbidden. Water had gone through the fenestron, taking the fenestron with it, which is the reason for the uncontrolled spin.
Tragically, the man on the winch died.
I don't remember it being in Taiwan, though. Again, I may be wrong.