The report has been released by the Nigerian FAA and is available from them.
The bottom line is that the helicopter suffered a TR failure on short finals resulting from a fatigue crack in one of the blade roots. Not surprisingly there are a number of conclusions drawn by the Nigerian investigators that have no basis.
The Captain is critiscised in the report for not ditching the helicopter after an uncommanded/unintentional inflation of the floats in the cruise. This is thought to be the most likely reason the helicopter was returning to it's point of departure at Brass. It was on the recovery on short finals that the catastrophic failure of the TR took place. Due to the speed and point at which the failure happened the helicopter spun violently out of control hitting a container positioned on a barge before landing upside down in the water.
The French DGAC were involved with the investigation and fortunately their findings have also been published in the report. As one would expect they have highlighted the sections of the report that they disagree with. Their main point being that the Captain's decision to return to Brass following the inadvertant inflation of the floats was a sound one. Flight with the floats deployed although unusual would not have presented a sufficient enough threat to the safety of the helicopter to prompt an immediate decision to ditch. Also there is no evidence to suggest that the crew had any symptoms that would have led them to believe that they were in danger of suffering the sudden loss of the tailrotor on short finals that actually resulted in the crash.
I can say with some degree of confidence that had the Captain chosen to ditch a helicopter that was perfectly seviceable just because the floats had inflated, he would have been severely criticised by the subsequent board of inquiry and been soley responsible for any loss of life that may have resulted during the ditching.
Under a different set of circumstancs the decision to ditch may have been the right one as was demonstrated by the successful ditching of a 365N2 in Indonesia earlier this week where the Captain put the helicopter in the water after experiencing severe vibration and the gradual loss of TR effectiveness. There were no injuries amongst the 6 on board who were picked up quickly by a rescue boat from their dinghies.