212 Man,
In a twin engined helicopter unable to hover OEI, following an engine failure where the collective is incorrectly RAISED (or not lowered)in an attempt to prevent descent following an engine failure an OVERPITCHED condition is the result.
Nr then decreases, likewise the tail rotor/fenestron RPM. The torque reaction is still there due to full power on remaining engine. Less effective fenestron due to reduced RPM equals yaw to the left for a French helicopter (main rotor clockwise seen from pilot's seat).
Splash one, with yaw left.
Fenestron drive fails due to overload whilst driving water. Engine then not driving fenestron = more power for main rotor and it may be possible to lift off once Nr recovered.
More yaw left and Splash Two.
(A single engined French helicopter would of course yaw RIGHT following engine failure).
Only problem is, this aircraft did not appear to be overpitched due to its flat coning angle. I would conclude a fenestron problem was the primary factor.