A&C
Having a very accurate starting point for the SAR services to start from has to be a major advantage during a search, an aircraft can glide a long way from 2000 ft and it is a very big sea when you are looking for a guy who is up to his neck in water, with all the airliners monitoring 121.5 this very accurate ditching position becomes available far beyond the range of the land based VHF triangulation system.
Not sure what your getting at here but yes I agree, thats why I made the original post about trying to let ATC know at the earliest opportunity as to the predicament you are in......and yes after spending 20 years as a voulanteer lifeboat Coxwain I also agree about a guy up to his neck in the water is very difficult to see!