Everybody I've ever talked to who'd done this "actual," flared and pulled pitch higher than they thought they were. The water's a very poor surface to judge altitude from. I'd guess that all the fancy talk of rolling left, right, landing on the crest, etc. is not realistic- falling from 10+ feet with decaying RPM is going throw the timing and effect off.
SO- I'd do a HUET for sure.
I'd want floats.
I'd have my vest and survival gear on at all times.
I'd prebrief everybody and hope they're adequately trained.
With small seas running, I'd go into the wind and ZERO forward motion at touchdown, and parallel the swells if they're significant, with ZERO forward motion at touchdown.
ZERO forward motion, I think is the prime consideration. It's important enough that I'd ditch with power if ditching was certain rather than risk the trend to fall from height. It'd be tough, but sometimes there are no good answers, only some better than others.
Hitting with forward momentum will tend to bring the heavy and rotating stuff into the cabin and that's very bad.
ZERO forward momentum, more than rolling left, tail first etc. is my aim. Hitting with minimum vertical impact would be next consideration.
Having the doors open is a nice thought. The pilot flying probably won't have time, and the pax will probably be involved in cinching tight, etc., so be prepared to jettison underwater and/or kick panels out...