A non violent impact or a "Sully ditching" would imply a calm sea, nose-up attitude between 5 and 10 degrees and low rate of descent. That could only be achieved with the slats and flaps extended
I agree that a "Sully ditching" requires a conscious pilot and a benign seastate. Furthermore, that pilot must be able to think beyond normal procedures and to anticipate what is required for a successful ditching with engines out. However, a nose-up attitude between 5 and 10 degrees and low rate of descent can be achieved with the slats and flaps retracted.