A good first port of call would be a paper written by the RHOSS committee entitled CAP 641 Report of the Review of Helicopter Offshore Safety and Survivability; this can be found at:
http://www.caa.co.uk/publications/pu...ils.asp?id=138
You should be aware that you might have to be careful with any searches that you do (and any information that is returned): ICAO and most States do not require an engine failure to be reported; if that engine failure is then followed by a ditching (landing on the water) which does not result in injury or damage beyond a certain threshold, it will not be recorded as an accident or in some cases an incident.