I've never ditched, but the accepted teaching when I learned to fly rotary was to get the rear doors open, then to zero-speed into the water, hold it upright as long as possible, and then if there was a choice, roll it so that the advancing blade would hit the water, supposedly reducing the likelihood of the transmission ripping off its mounts and taking out the passengers strapped onto the centre rear cabin wall (this was in B204/205s).
Sounded fair to me at the time.